Down-integrate from google3.

45 files changed, 797 insertions, 412 deletions

diff --git a/java/core/src/main/java/com/google/protobuf/AbstractMessage.java b/java/core/src/main/java/com/google/protobuf/AbstractMessage.java
index fc3c2a5d..09aaed18 100644
--- a/java/core/src/main/java/com/google/protobuf/AbstractMessage.java
+++ b/java/core/src/main/java/com/google/protobuf/AbstractMessage.java
@@ -32,7 +32,6 @@ package com.google.protobuf;
 
 import com.google.protobuf.Descriptors.EnumValueDescriptor;
 import com.google.protobuf.Descriptors.FieldDescriptor;
-import com.google.protobuf.Descriptors.FileDescriptor.Syntax;
 import com.google.protobuf.Descriptors.OneofDescriptor;
 import com.google.protobuf.Internal.EnumLite;
 import java.io.IOException;
@@ -446,10 +445,7 @@ public abstract class AbstractMessage
         final CodedInputStream input,
         final ExtensionRegistryLite extensionRegistry)
         throws IOException {
-      boolean discardUnknown =
-          getDescriptorForType().getFile().getSyntax() == Syntax.PROTO3
-              ? input.shouldDiscardUnknownFieldsProto3()
-              : input.shouldDiscardUnknownFields();
+      boolean discardUnknown = input.shouldDiscardUnknownFields();
       final UnknownFieldSet.Builder unknownFields =
           discardUnknown ? null : UnknownFieldSet.newBuilder(getUnknownFields());
       while (true) {
diff --git a/java/core/src/main/java/com/google/protobuf/BooleanArrayList.java b/java/core/src/main/java/com/google/protobuf/BooleanArrayList.java
index 4d7a9727..0dedb173 100644
--- a/java/core/src/main/java/com/google/protobuf/BooleanArrayList.java
+++ b/java/core/src/main/java/com/google/protobuf/BooleanArrayList.java
@@ -42,7 +42,8 @@ import java.util.RandomAccess;
  *
  * @author dweis@google.com (Daniel Weis)
  */
-final class BooleanArrayList extends AbstractProtobufList<Boolean>
+final class BooleanArrayList
+    extends AbstractProtobufList<Boolean>
     implements BooleanList, RandomAccess, PrimitiveNonBoxingCollection {
 
   private static final BooleanArrayList EMPTY_LIST = new BooleanArrayList();
diff --git a/java/core/src/main/java/com/google/protobuf/ByteString.java b/java/core/src/main/java/com/google/protobuf/ByteString.java
index d67bb54a..ddda0f26 100644
--- a/java/core/src/main/java/com/google/protobuf/ByteString.java
+++ b/java/core/src/main/java/com/google/protobuf/ByteString.java
@@ -46,6 +46,7 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.Comparator;
 import java.util.Iterator;
 import java.util.List;
 import java.util.NoSuchElementException;
@@ -222,6 +223,67 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
   }
 
   // =================================================================
+  // Comparison
+
+  private static final int UNSIGNED_BYTE_MASK = 0xFF;
+
+  /**
+   * Returns the value of the given byte as an integer, interpreting the byte as an unsigned value.
+   * That is, returns {@code value + 256} if {@code value} is negative; {@code value} itself
+   * otherwise.
+   *
+   * <p>Note: This code was copied from {@link com.google.common.primitives.UnsignedBytes#toInt}, as
+   * Guava libraries cannot be used in the {@code com.google.protobuf} package.
+   */
+  private static int toInt(byte value) {
+    return value & UNSIGNED_BYTE_MASK;
+  }
+
+  /**
+   * Compares two {@link ByteString}s lexicographically, treating their contents as unsigned byte
+   * values between 0 and 255 (inclusive).
+   *
+   * <p>For example, {@code (byte) -1} is considered to be greater than {@code (byte) 1} because
+   * it is interpreted as an unsigned value, {@code 255}.
+   */
+  private static final Comparator<ByteString> UNSIGNED_LEXICOGRAPHICAL_COMPARATOR =
+      new Comparator<ByteString>() {
+        @Override
+        public int compare(ByteString former, ByteString latter) {
+          ByteIterator formerBytes = former.iterator();
+          ByteIterator latterBytes = latter.iterator();
+
+          while (formerBytes.hasNext() && latterBytes.hasNext()) {
+            // Note: This code was copied from com.google.common.primitives.UnsignedBytes#compare,
+            // as Guava libraries cannot be used in the {@code com.google.protobuf} package.
+            int result =
+                Integer.compare(toInt(formerBytes.nextByte()), toInt(latterBytes.nextByte()));
+            if (result != 0) {
+              return result;
+            }
+          }
+
+          return Integer.compare(former.size(), latter.size());
+        }
+      };
+
+  /**
+   * Returns a {@link Comparator<ByteString>} which compares {@link ByteString}-s lexicographically
+   * as sequences of unsigned bytes (i.e. values between 0 and 255, inclusive).
+   *
+   * <p>For example, {@code (byte) -1} is considered to be greater than {@code (byte) 1} because
+   * it is interpreted as an unsigned value, {@code 255}:
+   *
+   * <ul>
+   * <li>{@code `-1` -> 0b11111111 (two's complement) -> 255}
+   * <li>{@code `1` -> 0b00000001 -> 1}
+   * </ul>
+   */
+  public static Comparator<ByteString> unsignedLexicographicalComparator() {
+    return UNSIGNED_LEXICOGRAPHICAL_COMPARATOR;
+  }
+
+  // =================================================================
   // ByteString -> substring
 
   /**
@@ -287,8 +349,10 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    * @param offset offset in source array
    * @param size number of bytes to copy
    * @return new {@code ByteString}
+   * @throws IndexOutOfBoundsException if {@code offset} or {@code size} are out of bounds
    */
   public static ByteString copyFrom(byte[] bytes, int offset, int size) {
+    checkRange(offset, offset + size, bytes.length);
     return new LiteralByteString(byteArrayCopier.copyFrom(bytes, offset, size));
   }
 
@@ -339,8 +403,10 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
    * @param bytes source buffer
    * @param size number of bytes to copy
    * @return new {@code ByteString}
+   * @throws IndexOutOfBoundsException if {@code size > bytes.remaining()}
    */
   public static ByteString copyFrom(ByteBuffer bytes, int size) {
+    checkRange(0, size, bytes.remaining());
     byte[] copy = new byte[size];
     bytes.get(copy);
     return new LiteralByteString(copy);
@@ -578,6 +644,9 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
   /**
    * Copies bytes into a buffer at the given offset.
    *
+   * <p>To copy a subset of bytes, you call this method on the return value of {@link
+   * #substring(int, int)}. Example: {@code byteString.substring(start, end).copyTo(target, offset)}
+   *
    * @param target buffer to copy into
    * @param offset in the target buffer
    * @throws IndexOutOfBoundsException if the offset is negative or too large
@@ -589,15 +658,16 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
   /**
    * Copies bytes into a buffer.
    *
-   * @param target       buffer to copy into
+   * @param target buffer to copy into
    * @param sourceOffset offset within these bytes
    * @param targetOffset offset within the target buffer
    * @param numberToCopy number of bytes to copy
-   * @throws IndexOutOfBoundsException if an offset or size is negative or too
-   *     large
+   * @throws IndexOutOfBoundsException if an offset or size is negative or too large
+   * @deprecation Instead, call {@code byteString.substring(sourceOffset, sourceOffset +
+   *     numberToCopy).copyTo(target, targetOffset)}
    */
-  public final void copyTo(byte[] target, int sourceOffset, int targetOffset,
-      int numberToCopy) {
+  @Deprecated
+  public final void copyTo(byte[] target, int sourceOffset, int targetOffset, int numberToCopy) {
     checkRange(sourceOffset, sourceOffset + numberToCopy, size());
     checkRange(targetOffset, targetOffset + numberToCopy, target.length);
     if (numberToCopy > 0) {
@@ -617,10 +687,13 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
   /**
    * Copies bytes into a ByteBuffer.
    *
+   * <p>To copy a subset of bytes, you call this method on the return value of {@link
+   * #substring(int, int)}. Example: {@code byteString.substring(start, end).copyTo(target)}
+   *
    * @param target ByteBuffer to copy into.
    * @throws java.nio.ReadOnlyBufferException if the {@code target} is read-only
-   * @throws java.nio.BufferOverflowException if the {@code target}'s
-   *     remaining() space is not large enough to hold the data.
+   * @throws java.nio.BufferOverflowException if the {@code target}'s remaining() space is not large
+   *     enough to hold the data.
    */
   public abstract void copyTo(ByteBuffer target);
 
@@ -1258,6 +1331,9 @@ public abstract class ByteString implements Iterable<Byte>, Serializable {
      * @param bytes array to wrap
      */
     LiteralByteString(byte[] bytes) {
+      if (bytes == null) {
+        throw new NullPointerException();
+      }
       this.bytes = bytes;
     }
 
diff --git a/java/core/src/main/java/com/google/protobuf/CodedInputStream.java b/java/core/src/main/java/com/google/protobuf/CodedInputStream.java
index 1297462e..4545d0ae 100644
--- a/java/core/src/main/java/com/google/protobuf/CodedInputStream.java
+++ b/java/core/src/main/java/com/google/protobuf/CodedInputStream.java
@@ -64,12 +64,6 @@ public abstract class CodedInputStream {
   // Integer.MAX_VALUE == 0x7FFFFFF == INT_MAX from limits.h
   private static final int DEFAULT_SIZE_LIMIT = Integer.MAX_VALUE;
 
-  /**
-   * Whether to enable our custom UTF-8 decode codepath which does not use {@link StringCoding}.
-   * Currently disabled.
-   */
-  private static final boolean ENABLE_CUSTOM_UTF8_DECODE = false;
-
   /** Visible for subclasses. See setRecursionLimit() */
   int recursionDepth;
 
@@ -417,21 +411,7 @@ public abstract class CodedInputStream {
   }
 
 
-  private boolean explicitDiscardUnknownFields = false;
-
-  private static volatile boolean proto3DiscardUnknownFieldsDefault = false;
-
-  static void setProto3DiscardUnknownsByDefaultForTest() {
-    proto3DiscardUnknownFieldsDefault = true;
-  }
-
-  static void setProto3KeepUnknownsByDefaultForTest() {
-    proto3DiscardUnknownFieldsDefault = false;
-  }
-
-  static boolean getProto3DiscardUnknownFieldsDefault() {
-    return proto3DiscardUnknownFieldsDefault;
-  }
+  private boolean shouldDiscardUnknownFields = false;
 
   /**
    * Sets this {@code CodedInputStream} to discard unknown fields. Only applies to full runtime
@@ -442,7 +422,7 @@ public abstract class CodedInputStream {
    * runtime.
    */
   final void discardUnknownFields() {
-    explicitDiscardUnknownFields = true;
+    shouldDiscardUnknownFields = true;
   }
 
   /**
@@ -450,7 +430,7 @@ public abstract class CodedInputStream {
    * default.
    */
   final void unsetDiscardUnknownFields() {
-    explicitDiscardUnknownFields = false;
+    shouldDiscardUnknownFields = false;
   }
 
   /**
@@ -458,19 +438,7 @@ public abstract class CodedInputStream {
    * runtime messages.
    */
   final boolean shouldDiscardUnknownFields() {
-    return explicitDiscardUnknownFields;
-  }
-
-  /**
-   * Whether unknown fields in this input stream should be discarded during parsing for proto3 full
-   * runtime messages.
-   *
-   * <p>This function was temporarily introduced before proto3 unknown fields behavior is changed.
-   * TODO(liujisi): remove this and related code in GeneratedMessage after proto3 unknown
-   * fields migration is done.
-   */
-  final boolean shouldDiscardUnknownFieldsProto3() {
-    return explicitDiscardUnknownFields ? true : proto3DiscardUnknownFieldsDefault;
+    return shouldDiscardUnknownFields;
   }
 
   /**
@@ -831,19 +799,9 @@ public abstract class CodedInputStream {
     public String readStringRequireUtf8() throws IOException {
       final int size = readRawVarint32();
       if (size > 0 && size <= (limit - pos)) {
-        if (ENABLE_CUSTOM_UTF8_DECODE) {
-          String result = Utf8.decodeUtf8(buffer, pos, size);
-          pos += size;
-          return result;
-        } else {
-          // TODO(martinrb): We could save a pass by validating while decoding.
-          if (!Utf8.isValidUtf8(buffer, pos, pos + size)) {
-            throw InvalidProtocolBufferException.invalidUtf8();
-          }
-          final int tempPos = pos;
-          pos += size;
-          return new String(buffer, tempPos, size, UTF_8);
-        }
+        String result = Utf8.decodeUtf8(buffer, pos, size);
+        pos += size;
+        return result;
       }
 
       if (size == 0) {
@@ -1559,25 +1517,10 @@ public abstract class CodedInputStream {
     public String readStringRequireUtf8() throws IOException {
       final int size = readRawVarint32();
       if (size > 0 && size <= remaining()) {
-        if (ENABLE_CUSTOM_UTF8_DECODE) {
-          final int bufferPos = bufferPos(pos);
-          String result = Utf8.decodeUtf8(buffer, bufferPos, size);
-          pos += size;
-          return result;
-        } else {
-          // TODO(nathanmittler): Is there a way to avoid this copy?
-          // The same as readBytes' logic
-          byte[] bytes = new byte[size];
-          UnsafeUtil.copyMemory(pos, bytes, 0, size);
-          // TODO(martinrb): We could save a pass by validating while decoding.
-          if (!Utf8.isValidUtf8(bytes)) {
-            throw InvalidProtocolBufferException.invalidUtf8();
-          }
-
-          String result = new String(bytes, UTF_8);
-          pos += size;
-          return result;
-        }
+        final int bufferPos = bufferPos(pos);
+        String result = Utf8.decodeUtf8(buffer, bufferPos, size);
+        pos += size;
+        return result;
       }
 
       if (size == 0) {
@@ -2345,15 +2288,7 @@ public abstract class CodedInputStream {
         bytes = readRawBytesSlowPath(size);
         tempPos = 0;
       }
-      if (ENABLE_CUSTOM_UTF8_DECODE) {
-        return Utf8.decodeUtf8(bytes, tempPos, size);
-      } else {
-        // TODO(martinrb): We could save a pass by validating while decoding.
-        if (!Utf8.isValidUtf8(bytes, tempPos, tempPos + size)) {
-          throw InvalidProtocolBufferException.invalidUtf8();
-        }
-        return new String(bytes, tempPos, size, UTF_8);
-      }
+      return Utf8.decodeUtf8(bytes, tempPos, size);
     }
 
     @Override
@@ -3373,34 +3308,15 @@ public abstract class CodedInputStream {
     public String readStringRequireUtf8() throws IOException {
       final int size = readRawVarint32();
       if (size > 0 && size <= currentByteBufferLimit - currentByteBufferPos) {
-        if (ENABLE_CUSTOM_UTF8_DECODE) {
-          final int bufferPos = (int) (currentByteBufferPos - currentByteBufferStartPos);
-          String result = Utf8.decodeUtf8(currentByteBuffer, bufferPos, size);
-          currentByteBufferPos += size;
-          return result;
-        } else {
-          byte[] bytes = new byte[size];
-          UnsafeUtil.copyMemory(currentByteBufferPos, bytes, 0, size);
-          if (!Utf8.isValidUtf8(bytes)) {
-            throw InvalidProtocolBufferException.invalidUtf8();
-          }
-          String result = new String(bytes, UTF_8);
-          currentByteBufferPos += size;
-          return result;
-        }
+        final int bufferPos = (int) (currentByteBufferPos - currentByteBufferStartPos);
+        String result = Utf8.decodeUtf8(currentByteBuffer, bufferPos, size);
+        currentByteBufferPos += size;
+        return result;
       }
       if (size >= 0 && size <= remaining()) {
         byte[] bytes = new byte[size];
         readRawBytesTo(bytes, 0, size);
-        if (ENABLE_CUSTOM_UTF8_DECODE) {
-          return Utf8.decodeUtf8(bytes, 0, size);
-        } else {
-          if (!Utf8.isValidUtf8(bytes)) {
-            throw InvalidProtocolBufferException.invalidUtf8();
-          }
-          String result = new String(bytes, UTF_8);
-          return result;
-        }
+        return Utf8.decodeUtf8(bytes, 0, size);
       }
 
       if (size == 0) {
diff --git a/java/core/src/main/java/com/google/protobuf/DoubleArrayList.java b/java/core/src/main/java/com/google/protobuf/DoubleArrayList.java
index 5b28b4a8..8d987b2e 100644
--- a/java/core/src/main/java/com/google/protobuf/DoubleArrayList.java
+++ b/java/core/src/main/java/com/google/protobuf/DoubleArrayList.java
@@ -42,7 +42,8 @@ import java.util.RandomAccess;
  *
  * @author dweis@google.com (Daniel Weis)
  */
-final class DoubleArrayList extends AbstractProtobufList<Double>
+final class DoubleArrayList
+    extends AbstractProtobufList<Double>
     implements DoubleList, RandomAccess, PrimitiveNonBoxingCollection {
 
   private static final DoubleArrayList EMPTY_LIST = new DoubleArrayList();
diff --git a/java/core/src/main/java/com/google/protobuf/DynamicMessage.java b/java/core/src/main/java/com/google/protobuf/DynamicMessage.java
index a6a774b7..2c346e03 100644
--- a/java/core/src/main/java/com/google/protobuf/DynamicMessage.java
+++ b/java/core/src/main/java/com/google/protobuf/DynamicMessage.java
@@ -608,20 +608,12 @@ public final class DynamicMessage extends AbstractMessage {
 
     @Override
     public Builder setUnknownFields(UnknownFieldSet unknownFields) {
-      if (getDescriptorForType().getFile().getSyntax() == Descriptors.FileDescriptor.Syntax.PROTO3
-          && CodedInputStream.getProto3DiscardUnknownFieldsDefault()) {
-        return this;
-      }
       this.unknownFields = unknownFields;
       return this;
     }
 
     @Override
     public Builder mergeUnknownFields(UnknownFieldSet unknownFields) {
-      if (getDescriptorForType().getFile().getSyntax() == Descriptors.FileDescriptor.Syntax.PROTO3
-          && CodedInputStream.getProto3DiscardUnknownFieldsDefault()) {
-        return this;
-      }
       this.unknownFields =
         UnknownFieldSet.newBuilder(this.unknownFields)
                        .mergeFrom(unknownFields)
diff --git a/java/core/src/main/java/com/google/protobuf/FloatArrayList.java b/java/core/src/main/java/com/google/protobuf/FloatArrayList.java
index 7c080af3..41749f6d 100644
--- a/java/core/src/main/java/com/google/protobuf/FloatArrayList.java
+++ b/java/core/src/main/java/com/google/protobuf/FloatArrayList.java
@@ -42,7 +42,8 @@ import java.util.RandomAccess;
  *
  * @author dweis@google.com (Daniel Weis)
  */
-final class FloatArrayList extends AbstractProtobufList<Float>
+final class FloatArrayList
+    extends AbstractProtobufList<Float>
     implements FloatList, RandomAccess, PrimitiveNonBoxingCollection {
 
   private static final FloatArrayList EMPTY_LIST = new FloatArrayList();
diff --git a/java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java b/java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java
index df01547e..35b31f15 100644
--- a/java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java
+++ b/java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java
@@ -33,7 +33,6 @@ package com.google.protobuf;
 import com.google.protobuf.AbstractMessageLite.Builder.LimitedInputStream;
 import com.google.protobuf.Internal.BooleanList;
 import com.google.protobuf.Internal.DoubleList;
-import com.google.protobuf.Internal.EnumLiteMap;
 import com.google.protobuf.Internal.FloatList;
 import com.google.protobuf.Internal.IntList;
 import com.google.protobuf.Internal.LongList;
@@ -1600,7 +1599,7 @@ public abstract class GeneratedMessageLite<
   protected static class DefaultInstanceBasedParser<T extends GeneratedMessageLite<T, ?>>
       extends AbstractParser<T> {
 
-    private T defaultInstance;
+    private final T defaultInstance;
 
     public DefaultInstanceBasedParser(T defaultInstance) {
       this.defaultInstance = defaultInstance;
diff --git a/java/core/src/main/java/com/google/protobuf/GeneratedMessageV3.java b/java/core/src/main/java/com/google/protobuf/GeneratedMessageV3.java
index 4acd8f2f..53af544f 100644
--- a/java/core/src/main/java/com/google/protobuf/GeneratedMessageV3.java
+++ b/java/core/src/main/java/com/google/protobuf/GeneratedMessageV3.java
@@ -38,6 +38,11 @@ import com.google.protobuf.Descriptors.EnumValueDescriptor;
 import com.google.protobuf.Descriptors.FieldDescriptor;
 import com.google.protobuf.Descriptors.FileDescriptor;
 import com.google.protobuf.Descriptors.OneofDescriptor;
+import com.google.protobuf.Internal.BooleanList;
+import com.google.protobuf.Internal.DoubleList;
+import com.google.protobuf.Internal.FloatList;
+import com.google.protobuf.Internal.IntList;
+import com.google.protobuf.Internal.LongList;
 // In opensource protobuf, we have versioned this GeneratedMessageV3 class to GeneratedMessageV3V3 and
 // in the future may have GeneratedMessageV3V4 etc. This allows us to change some aspects of this
 // class without breaking binary compatibility with old generated code that still subclasses
@@ -293,16 +298,17 @@ public abstract class GeneratedMessageV3 extends AbstractMessage
     return unknownFields.mergeFieldFrom(tag, input);
   }
 
+  /**
+   * Delegates to parseUnknownField. This method is obsolete, but we must retain it for
+   * compatibility with older generated code.
+   */
   protected boolean parseUnknownFieldProto3(
       CodedInputStream input,
       UnknownFieldSet.Builder unknownFields,
       ExtensionRegistryLite extensionRegistry,
       int tag)
       throws IOException {
-    if (input.shouldDiscardUnknownFieldsProto3()) {
-      return input.skipField(tag);
-    }
-    return unknownFields.mergeFieldFrom(tag, input);
+    return parseUnknownField(input, unknownFields, extensionRegistry, tag);
   }
 
   protected static <M extends Message> M parseWithIOException(Parser<M> parser, InputStream input)
@@ -363,6 +369,76 @@ public abstract class GeneratedMessageV3 extends AbstractMessage
     return UnsafeUtil.hasUnsafeArrayOperations() && UnsafeUtil.hasUnsafeByteBufferOperations();
   }
 
+  protected static IntList emptyIntList() {
+    return IntArrayList.emptyList();
+  }
+
+  protected static IntList newIntList() {
+    return new IntArrayList();
+  }
+
+  protected static IntList mutableCopy(IntList list) {
+    int size = list.size();
+    return list.mutableCopyWithCapacity(
+        size == 0 ? AbstractProtobufList.DEFAULT_CAPACITY : size * 2);
+  }
+
+  protected static LongList emptyLongList() {
+    return LongArrayList.emptyList();
+  }
+
+  protected static LongList newLongList() {
+    return new LongArrayList();
+  }
+
+  protected static LongList mutableCopy(LongList list) {
+    int size = list.size();
+    return list.mutableCopyWithCapacity(
+        size == 0 ? AbstractProtobufList.DEFAULT_CAPACITY : size * 2);
+  }
+
+  protected static FloatList emptyFloatList() {
+    return FloatArrayList.emptyList();
+  }
+
+  protected static FloatList newFloatList() {
+    return new FloatArrayList();
+  }
+
+  protected static FloatList mutableCopy(FloatList list) {
+    int size = list.size();
+    return list.mutableCopyWithCapacity(
+        size == 0 ? AbstractProtobufList.DEFAULT_CAPACITY : size * 2);
+  }
+
+  protected static DoubleList emptyDoubleList() {
+    return DoubleArrayList.emptyList();
+  }
+
+  protected static DoubleList newDoubleList() {
+    return new DoubleArrayList();
+  }
+
+  protected static DoubleList mutableCopy(DoubleList list) {
+    int size = list.size();
+    return list.mutableCopyWithCapacity(
+        size == 0 ? AbstractProtobufList.DEFAULT_CAPACITY : size * 2);
+  }
+
+  protected static BooleanList emptyBooleanList() {
+    return BooleanArrayList.emptyList();
+  }
+
+  protected static BooleanList newBooleanList() {
+    return new BooleanArrayList();
+  }
+
+  protected static BooleanList mutableCopy(BooleanList list) {
+    int size = list.size();
+    return list.mutableCopyWithCapacity(
+        size == 0 ? AbstractProtobufList.DEFAULT_CAPACITY : size * 2);
+  }
+
   @Override
   public void writeTo(final CodedOutputStream output) throws IOException {
     MessageReflection.writeMessageTo(this, getAllFieldsRaw(), output, false);
@@ -641,13 +717,12 @@ public abstract class GeneratedMessageV3 extends AbstractMessage
       return (BuilderType) this;
     }
 
+    /**
+     * Delegates to setUnknownFields. This method is obsolete, but we must retain it for
+     * compatibility with older generated code.
+     */
     protected BuilderType setUnknownFieldsProto3(final UnknownFieldSet unknownFields) {
-      if (CodedInputStream.getProto3DiscardUnknownFieldsDefault()) {
-        return (BuilderType) this;
-      }
-      this.unknownFields = unknownFields;
-      onChanged();
-      return (BuilderType) this;
+      return setUnknownFields(unknownFields);
     }
 
     @Override
@@ -1009,19 +1084,17 @@ public abstract class GeneratedMessageV3 extends AbstractMessage
           getDescriptorForType(), new MessageReflection.ExtensionAdapter(extensions), tag);
     }
 
+    /**
+     * Delegates to parseUnknownField. This method is obsolete, but we must retain it for
+     * compatibility with older generated code.
+     */
     @Override
     protected boolean parseUnknownFieldProto3(
         CodedInputStream input,
         UnknownFieldSet.Builder unknownFields,
         ExtensionRegistryLite extensionRegistry,
         int tag) throws IOException {
-      return MessageReflection.mergeFieldFrom(
-          input,
-          input.shouldDiscardUnknownFieldsProto3() ? null : unknownFields,
-          extensionRegistry,
-          getDescriptorForType(),
-          new MessageReflection.ExtensionAdapter(extensions),
-          tag);
+      return parseUnknownField(input, unknownFields, extensionRegistry, tag);
     }
 
 
diff --git a/java/core/src/main/java/com/google/protobuf/IntArrayList.java b/java/core/src/main/java/com/google/protobuf/IntArrayList.java
index aacd71e1..4993eea7 100644
--- a/java/core/src/main/java/com/google/protobuf/IntArrayList.java
+++ b/java/core/src/main/java/com/google/protobuf/IntArrayList.java
@@ -42,7 +42,8 @@ import java.util.RandomAccess;
  *
  * @author dweis@google.com (Daniel Weis)
  */
-final class IntArrayList extends AbstractProtobufList<Integer>
+final class IntArrayList
+    extends AbstractProtobufList<Integer>
     implements IntList, RandomAccess, PrimitiveNonBoxingCollection {
 
   private static final IntArrayList EMPTY_LIST = new IntArrayList();
diff --git a/java/core/src/main/java/com/google/protobuf/Internal.java b/java/core/src/main/java/com/google/protobuf/Internal.java
index 848cad03..878573d5 100644
--- a/java/core/src/main/java/com/google/protobuf/Internal.java
+++ b/java/core/src/main/java/com/google/protobuf/Internal.java
@@ -234,6 +234,11 @@ public final class Internal {
     T findValueByNumber(int number);
   }
 
+  /** Interface for an object which verifies integers are in range. */
+  public interface EnumVerifier {
+    boolean isInRange(int number);
+  }
+
   /**
    * Helper method for implementing {@link Message#hashCode()} for longs.
    * @see Long#hashCode()
diff --git a/java/core/src/main/java/com/google/protobuf/LazyStringArrayList.java b/java/core/src/main/java/com/google/protobuf/LazyStringArrayList.java
index d474c51e..6cfc14a5 100644
--- a/java/core/src/main/java/com/google/protobuf/LazyStringArrayList.java
+++ b/java/core/src/main/java/com/google/protobuf/LazyStringArrayList.java
@@ -69,7 +69,7 @@ public class LazyStringArrayList extends AbstractProtobufList<String>
   static {
     EMPTY_LIST.makeImmutable();
   }
-  
+
   static LazyStringArrayList emptyList() {
     return EMPTY_LIST;
   }
@@ -83,8 +83,8 @@ public class LazyStringArrayList extends AbstractProtobufList<String>
     this(DEFAULT_CAPACITY);
   }
 
-  public LazyStringArrayList(int intialCapacity) {
-    this(new ArrayList<Object>(intialCapacity));
+  public LazyStringArrayList(int initialCapacity) {
+    this(new ArrayList<Object>(initialCapacity));
   }
 
   public LazyStringArrayList(LazyStringList from) {
@@ -95,7 +95,7 @@ public class LazyStringArrayList extends AbstractProtobufList<String>
   public LazyStringArrayList(List<String> from) {
     this(new ArrayList<Object>(from));
   }
-  
+
   private LazyStringArrayList(ArrayList<Object> list) {
     this.list = list;
   }
@@ -150,13 +150,13 @@ public class LazyStringArrayList extends AbstractProtobufList<String>
     list.add(index, element);
     modCount++;
   }
-  
+
   private void add(int index, ByteString element) {
     ensureIsMutable();
     list.add(index, element);
     modCount++;
   }
-  
+
   private void add(int index, byte[] element) {
     ensureIsMutable();
     list.add(index, element);
@@ -221,7 +221,7 @@ public class LazyStringArrayList extends AbstractProtobufList<String>
     list.add(element);
     modCount++;
   }
-  
+
   @Override
   public void add(byte[] element) {
     ensureIsMutable();
@@ -233,7 +233,7 @@ public class LazyStringArrayList extends AbstractProtobufList<String>
   public Object getRaw(int index) {
     return list.get(index);
   }
-  
+
   @Override
   public ByteString getByteString(int index) {
     Object o = list.get(index);
@@ -243,7 +243,7 @@ public class LazyStringArrayList extends AbstractProtobufList<String>
     }
     return b;
   }
-  
+
   @Override
   public byte[] getByteArray(int index) {
     Object o = list.get(index);
@@ -258,7 +258,7 @@ public class LazyStringArrayList extends AbstractProtobufList<String>
   public void set(int index, ByteString s) {
     setAndReturn(index, s);
   }
-  
+
   private Object setAndReturn(int index, ByteString s) {
     ensureIsMutable();
     return list.set(index, s);
@@ -268,7 +268,7 @@ public class LazyStringArrayList extends AbstractProtobufList<String>
   public void set(int index, byte[] s) {
     setAndReturn(index, s);
   }
-  
+
   private Object setAndReturn(int index, byte[] s) {
     ensureIsMutable();
     return list.set(index, s);
@@ -283,7 +283,7 @@ public class LazyStringArrayList extends AbstractProtobufList<String>
       return Internal.toStringUtf8((byte[]) o);
     }
   }
-  
+
   private static ByteString asByteString(Object o) {
     if (o instanceof ByteString) {
       return (ByteString) o;
@@ -293,7 +293,7 @@ public class LazyStringArrayList extends AbstractProtobufList<String>
       return ByteString.copyFrom((byte[]) o);
     }
   }
-  
+
   private static byte[] asByteArray(Object o) {
     if (o instanceof byte[]) {
       return (byte[]) o;
@@ -327,11 +327,11 @@ public class LazyStringArrayList extends AbstractProtobufList<String>
   private static class ByteArrayListView extends AbstractList<byte[]>
       implements RandomAccess {
     private final LazyStringArrayList list;
-    
+
     ByteArrayListView(LazyStringArrayList list) {
       this.list = list;
     }
-    
+
     @Override
     public byte[] get(int index) {
       return list.getByteArray(index);
@@ -362,7 +362,7 @@ public class LazyStringArrayList extends AbstractProtobufList<String>
       return asByteArray(o);
     }
   }
-  
+
   @Override
   public List<byte[]> asByteArrayList() {
     return new ByteArrayListView(this);
diff --git a/java/core/src/main/java/com/google/protobuf/LongArrayList.java b/java/core/src/main/java/com/google/protobuf/LongArrayList.java
index 95945cb7..9a5056be 100644
--- a/java/core/src/main/java/com/google/protobuf/LongArrayList.java
+++ b/java/core/src/main/java/com/google/protobuf/LongArrayList.java
@@ -42,7 +42,8 @@ import java.util.RandomAccess;
  *
  * @author dweis@google.com (Daniel Weis)
  */
-final class LongArrayList extends AbstractProtobufList<Long>
+final class LongArrayList
+    extends AbstractProtobufList<Long>
     implements LongList, RandomAccess, PrimitiveNonBoxingCollection {
 
   private static final LongArrayList EMPTY_LIST = new LongArrayList();
diff --git a/java/core/src/main/java/com/google/protobuf/RepeatedFieldBuilder.java b/java/core/src/main/java/com/google/protobuf/RepeatedFieldBuilder.java
index 29f567dc..b593b566 100644
--- a/java/core/src/main/java/com/google/protobuf/RepeatedFieldBuilder.java
+++ b/java/core/src/main/java/com/google/protobuf/RepeatedFieldBuilder.java
@@ -30,6 +30,8 @@
 
 package com.google.protobuf;
 
+import static com.google.protobuf.Internal.checkNotNull;
+
 import java.util.AbstractList;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -290,9 +292,7 @@ public class RepeatedFieldBuilder
    */
   public RepeatedFieldBuilder<MType, BType, IType> setMessage(
       int index, MType message) {
-    if (message == null) {
-      throw new NullPointerException();
-    }
+    checkNotNull(message);
     ensureMutableMessageList();
     messages.set(index, message);
     if (builders != null) {
@@ -315,9 +315,7 @@ public class RepeatedFieldBuilder
    */
   public RepeatedFieldBuilder<MType, BType, IType> addMessage(
       MType message) {
-    if (message == null) {
-      throw new NullPointerException();
-    }
+    checkNotNull(message);
     ensureMutableMessageList();
     messages.add(message);
     if (builders != null) {
@@ -339,9 +337,7 @@ public class RepeatedFieldBuilder
    */
   public RepeatedFieldBuilder<MType, BType, IType> addMessage(
       int index, MType message) {
-    if (message == null) {
-      throw new NullPointerException();
-    }
+    checkNotNull(message);
     ensureMutableMessageList();
     messages.add(index, message);
     if (builders != null) {
@@ -363,9 +359,7 @@ public class RepeatedFieldBuilder
   public RepeatedFieldBuilder<MType, BType, IType> addAllMessages(
       Iterable<? extends MType> values) {
     for (final MType value : values) {
-      if (value == null) {
-        throw new NullPointerException();
-      }
+      checkNotNull(value);
     }
 
     // If we can inspect the size, we can more efficiently add messages.
diff --git a/java/core/src/main/java/com/google/protobuf/SingleFieldBuilder.java b/java/core/src/main/java/com/google/protobuf/SingleFieldBuilder.java
index 941b5def..1f5ec8a2 100644
--- a/java/core/src/main/java/com/google/protobuf/SingleFieldBuilder.java
+++ b/java/core/src/main/java/com/google/protobuf/SingleFieldBuilder.java
@@ -30,6 +30,8 @@
 
 package com.google.protobuf;
 
+import static com.google.protobuf.Internal.checkNotNull;
+
 /**
  * {@code SingleFieldBuilder} implements a structure that a protocol
  * message uses to hold a single field of another protocol message. It supports
@@ -84,10 +86,7 @@ public class SingleFieldBuilder
       MType message,
       GeneratedMessage.BuilderParent parent,
       boolean isClean) {
-    if (message == null) {
-      throw new NullPointerException();
-    }
-    this.message = message;
+    this.message = checkNotNull(message);
     this.parent = parent;
     this.isClean = isClean;
   }
@@ -169,10 +168,7 @@ public class SingleFieldBuilder
    */
   public SingleFieldBuilder<MType, BType, IType> setMessage(
       MType message) {
-    if (message == null) {
-      throw new NullPointerException();
-    }
-    this.message = message;
+    this.message = checkNotNull(message);
     if (builder != null) {
       builder.dispose();
       builder = null;
diff --git a/java/core/src/main/java/com/google/protobuf/TextFormat.java b/java/core/src/main/java/com/google/protobuf/TextFormat.java
index 25c3474f..79962e08 100644
--- a/java/core/src/main/java/com/google/protobuf/TextFormat.java
+++ b/java/core/src/main/java/com/google/protobuf/TextFormat.java
@@ -1444,8 +1444,8 @@ public final class TextFormat {
           logger.warning(msg.toString());
       } else {
         String[] lineColumn = unknownFields.get(0).split(":");
-        throw new ParseException(Integer.valueOf(lineColumn[0]),
-            Integer.valueOf(lineColumn[1]), msg.toString());
+        throw new ParseException(
+            Integer.parseInt(lineColumn[0]), Integer.parseInt(lineColumn[1]), msg.toString());
       }
     }
 
diff --git a/java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java b/java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java
index 37d64633..b3fdebcb 100644
--- a/java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java
+++ b/java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java
@@ -786,6 +786,23 @@ public final class UnknownFieldSet implements MessageLite {
     }
 
     /**
+     * Serializes the message to a {@code ByteString} and returns it. This is just a trivial wrapper
+     * around {@link #writeTo(int, CodedOutputStream)}.
+     */
+    public ByteString toByteString(int fieldNumber) {
+      try {
+        // TODO(lukes): consider caching serialized size in a volatile long
+        final ByteString.CodedBuilder out =
+            ByteString.newCodedBuilder(getSerializedSize(fieldNumber));
+        writeTo(fieldNumber, out.getCodedOutput());
+        return out.build();
+      } catch (IOException e) {
+        throw new RuntimeException(
+            "Serializing to a ByteString should never fail with an IOException", e);
+      }
+    }
+
+    /**
      * Serializes the field, including field number, and writes it to
      * {@code output}.
      */
diff --git a/java/core/src/main/java/com/google/protobuf/UnsafeUtil.java b/java/core/src/main/java/com/google/protobuf/UnsafeUtil.java
index d84ef3c5..f822ce51 100644
--- a/java/core/src/main/java/com/google/protobuf/UnsafeUtil.java
+++ b/java/core/src/main/java/com/google/protobuf/UnsafeUtil.java
@@ -33,6 +33,7 @@ package com.google.protobuf;
 import java.lang.reflect.Field;
 import java.nio.Buffer;
 import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
 import java.security.AccessController;
 import java.security.PrivilegedExceptionAction;
 import java.util.logging.Level;
@@ -146,6 +147,10 @@ final class UnsafeUtil {
     return MEMORY_ACCESSOR.getObject(target, offset);
   }
 
+  static void putObject(Object target, long offset, Object value) {
+    MEMORY_ACCESSOR.putObject(target, offset, value);
+  }
+
   static byte getByte(byte[] target, long index) {
     return MEMORY_ACCESSOR.getByte(target, BYTE_ARRAY_BASE_OFFSET + index);
   }
@@ -370,12 +375,6 @@ final class UnsafeUtil {
     return field != null && field.getType() == long.class ? field : null;
   }
 
-  /** Finds the value field within a {@link String}. */
-  private static Field stringValueField() {
-    Field field = field(String.class, "value");
-    return field != null && field.getType() == char[].class ? field : null;
-  }
-
   /**
    * Returns the offset of the provided field, or {@code -1} if {@code sun.misc.Unsafe} is not
    * available.
diff --git a/java/core/src/main/java/com/google/protobuf/Utf8.java b/java/core/src/main/java/com/google/protobuf/Utf8.java
index de75fe6b..b4a81ca3 100644
--- a/java/core/src/main/java/com/google/protobuf/Utf8.java
+++ b/java/core/src/main/java/com/google/protobuf/Utf8.java
@@ -42,7 +42,6 @@ import static java.lang.Character.isSurrogatePair;
 import static java.lang.Character.toCodePoint;
 
 import java.nio.ByteBuffer;
-import java.util.Arrays;
 
 /**
  * A set of low-level, high-performance static utility methods related
@@ -87,7 +86,9 @@ final class Utf8 {
    * delegate for which all methods are delegated directly to.
    */
   private static final Processor processor =
-      UnsafeProcessor.isAvailable() ? new UnsafeProcessor() : new SafeProcessor();
+      (UnsafeProcessor.isAvailable() && !Android.isOnAndroidDevice())
+          ? new UnsafeProcessor()
+          : new SafeProcessor();
 
   /**
    * A mask used when performing unsafe reads to determine if a long value contains any non-ASCII
diff --git a/java/core/src/test/java/com/google/protobuf/AbstractMessageTest.java b/java/core/src/test/java/com/google/protobuf/AbstractMessageTest.java
index cb2d34eb..bb11bd0f 100644
--- a/java/core/src/test/java/com/google/protobuf/AbstractMessageTest.java
+++ b/java/core/src/test/java/com/google/protobuf/AbstractMessageTest.java
@@ -210,8 +210,8 @@ public class AbstractMessageTest extends TestCase {
     new TestUtil.ReflectionTester(TestAllTypes.getDescriptor(), null);
 
   TestUtil.ReflectionTester extensionsReflectionTester =
-    new TestUtil.ReflectionTester(TestAllExtensions.getDescriptor(),
-                                  TestUtil.getExtensionRegistry());
+      new TestUtil.ReflectionTester(
+          TestAllExtensions.getDescriptor(), TestUtil.getFullExtensionRegistry());
 
   public void testClear() throws Exception {
     AbstractMessageWrapper message =
diff --git a/java/core/src/test/java/com/google/protobuf/BooleanArrayListTest.java b/java/core/src/test/java/com/google/protobuf/BooleanArrayListTest.java
index 4906763c..febe8537 100644
--- a/java/core/src/test/java/com/google/protobuf/BooleanArrayListTest.java
+++ b/java/core/src/test/java/com/google/protobuf/BooleanArrayListTest.java
@@ -299,20 +299,22 @@ public class BooleanArrayListTest extends TestCase {
   }
 
   public void testRemoveEndOfCapacity() {
-    BooleanList toRemove = BooleanArrayList.emptyList().mutableCopyWithCapacity(1);
+    BooleanList toRemove =
+        BooleanArrayList.emptyList().mutableCopyWithCapacity(1);
     toRemove.addBoolean(true);
     toRemove.remove(0);
     assertEquals(0, toRemove.size());
   }
 
   public void testSublistRemoveEndOfCapacity() {
-    BooleanList toRemove = BooleanArrayList.emptyList().mutableCopyWithCapacity(1);
+    BooleanList toRemove =
+        BooleanArrayList.emptyList().mutableCopyWithCapacity(1);
     toRemove.addBoolean(true);
     toRemove.subList(0, 1).clear();
     assertEquals(0, toRemove.size());
   }
 
-  private void assertImmutable(BooleanArrayList list) {
+  private void assertImmutable(BooleanList list) {
 
     try {
       list.add(true);
diff --git a/java/core/src/test/java/com/google/protobuf/ByteStringTest.java b/java/core/src/test/java/com/google/protobuf/ByteStringTest.java
index be71f1f5..fc22955d 100644
--- a/java/core/src/test/java/com/google/protobuf/ByteStringTest.java
+++ b/java/core/src/test/java/com/google/protobuf/ByteStringTest.java
@@ -41,6 +41,7 @@ import java.nio.ByteBuffer;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Comparator;
 import java.util.Iterator;
 import java.util.List;
 import java.util.NoSuchElementException;
@@ -86,6 +87,40 @@ public class ByteStringTest extends TestCase {
     return left.length == right.length && isArrayRange(left, right, 0, left.length);
   }
 
+  public void testCompare_equalByteStrings_compareEqual() throws Exception {
+    byte[] referenceBytes = getTestBytes();
+    ByteString string1 = ByteString.copyFrom(referenceBytes);
+    ByteString string2 = ByteString.copyFrom(referenceBytes);
+
+    assertEquals(
+        "ByteString instances containing the same data must compare equal.",
+        0,
+        ByteString.unsignedLexicographicalComparator().compare(string1, string2));
+  }
+
+  public void testCompare_byteStringsSortLexicographically() throws Exception {
+    ByteString app = ByteString.copyFromUtf8("app");
+    ByteString apple = ByteString.copyFromUtf8("apple");
+    ByteString banana = ByteString.copyFromUtf8("banana");
+
+    Comparator<ByteString> comparator = ByteString.unsignedLexicographicalComparator();
+
+    assertTrue("ByteString(app) < ByteString(apple)", comparator.compare(app, apple) < 0);
+    assertTrue("ByteString(app) < ByteString(banana)", comparator.compare(app, banana) < 0);
+    assertTrue("ByteString(apple) < ByteString(banana)", comparator.compare(apple, banana) < 0);
+  }
+
+  public void testCompare_interpretsByteValuesAsUnsigned() throws Exception {
+    // Two's compliment of `-1` == 0b11111111 == 255
+    ByteString twoHundredFiftyFive = ByteString.copyFrom(new byte[] {-1});
+    // 0b00000001 == 1
+    ByteString one = ByteString.copyFrom(new byte[] {1});
+
+    assertTrue(
+        "ByteString comparison treats bytes as unsigned values",
+        ByteString.unsignedLexicographicalComparator().compare(one, twoHundredFiftyFive) < 0);
+  }
+
   public void testSubstring_BeginIndex() {
     byte[] bytes = getTestBytes();
     ByteString substring = ByteString.copyFrom(bytes).substring(500);
@@ -161,6 +196,34 @@ public class ByteStringTest extends TestCase {
         byteString, byteStringAlt);
   }
 
+  public void testCopyFrom_LengthTooBig() {
+    byte[] testBytes = getTestBytes(100);
+    try {
+      ByteString.copyFrom(testBytes, 0, 200);
+      fail("Should throw");
+    } catch (IndexOutOfBoundsException expected) {
+    }
+
+    try {
+      ByteString.copyFrom(testBytes, 99, 2);
+      fail();
+    } catch (IndexOutOfBoundsException expected) {
+    }
+
+    ByteBuffer buf = ByteBuffer.wrap(testBytes);
+    try {
+      ByteString.copyFrom(buf, 101);
+      fail();
+    } catch (IndexOutOfBoundsException expected) {
+    }
+
+    try {
+      ByteString.copyFrom(testBytes, -1, 10);
+      fail("Should throw");
+    } catch (IndexOutOfBoundsException expected) {
+    }
+  }
+
   public void testCopyTo_TargetOffset() {
     byte[] bytes = getTestBytes();
     ByteString byteString = ByteString.copyFrom(bytes);
@@ -761,6 +824,9 @@ public class ByteStringTest extends TestCase {
    * Tests ByteString uses Arrays based byte copier when running under Hotstop VM.
    */
   public void testByteArrayCopier() throws Exception {
+    if (Android.isOnAndroidDevice()) {
+      return;
+    }
     Field field = ByteString.class.getDeclaredField("byteArrayCopier");
     field.setAccessible(true);
     Object byteArrayCopier = field.get(null);
diff --git a/java/core/src/test/java/com/google/protobuf/DiscardUnknownFieldsTest.java b/java/core/src/test/java/com/google/protobuf/DiscardUnknownFieldsTest.java
index 0f09a51b..36c4611f 100644
--- a/java/core/src/test/java/com/google/protobuf/DiscardUnknownFieldsTest.java
+++ b/java/core/src/test/java/com/google/protobuf/DiscardUnknownFieldsTest.java
@@ -62,22 +62,17 @@ public class DiscardUnknownFieldsTest {
   }
 
   private static void testProto2Message(Message message) throws Exception {
-    assertUnknownFieldsDefaultPreserved(message);
+    assertUnknownFieldsPreserved(message);
     assertUnknownFieldsExplicitlyDiscarded(message);
     assertReuseCodedInputStreamPreserve(message);
     assertUnknownFieldsInUnknownFieldSetArePreserve(message);
   }
 
   private static void testProto3Message(Message message) throws Exception {
-    CodedInputStream.setProto3KeepUnknownsByDefaultForTest();
-    assertUnknownFieldsDefaultPreserved(message);
+    assertUnknownFieldsPreserved(message);
     assertUnknownFieldsExplicitlyDiscarded(message);
     assertReuseCodedInputStreamPreserve(message);
     assertUnknownFieldsInUnknownFieldSetArePreserve(message);
-    CodedInputStream.setProto3DiscardUnknownsByDefaultForTest();
-    assertUnknownFieldsDefaultDiscarded(message);
-    assertUnknownFieldsExplicitlyDiscarded(message);
-    assertUnknownFieldsInUnknownFieldSetAreDiscarded(message);
   }
 
   private static void assertReuseCodedInputStreamPreserve(Message message) throws Exception {
@@ -122,7 +117,7 @@ public class DiscardUnknownFieldsTest {
     assertEquals(message.getClass().getName(), 0, built.getSerializedSize());
   }
 
-  private static void assertUnknownFieldsDefaultPreserved(MessageLite message) throws Exception {
+  private static void assertUnknownFieldsPreserved(MessageLite message) throws Exception {
     {
       MessageLite parsed = message.getParserForType().parseFrom(payload);
       assertEquals(message.getClass().getName(), payload, parsed.toByteString());
@@ -134,18 +129,6 @@ public class DiscardUnknownFieldsTest {
     }
   }
 
-  private static void assertUnknownFieldsDefaultDiscarded(MessageLite message) throws Exception {
-    {
-      MessageLite parsed = message.getParserForType().parseFrom(payload);
-      assertEquals(message.getClass().getName(), 0, parsed.getSerializedSize());
-    }
-
-    {
-      MessageLite parsed = message.newBuilderForType().mergeFrom(payload).build();
-      assertEquals(message.getClass().getName(), 0, parsed.getSerializedSize());
-    }
-  }
-
   private static void assertUnknownFieldsExplicitlyDiscarded(Message message) throws Exception {
     Message parsed =
         DiscardUnknownFieldsParser.wrap(message.getParserForType()).parseFrom(payload);
diff --git a/java/core/src/test/java/com/google/protobuf/DoubleArrayListTest.java b/java/core/src/test/java/com/google/protobuf/DoubleArrayListTest.java
index 923d7f43..a4c2f5aa 100644
--- a/java/core/src/test/java/com/google/protobuf/DoubleArrayListTest.java
+++ b/java/core/src/test/java/com/google/protobuf/DoubleArrayListTest.java
@@ -78,10 +78,10 @@ public class DoubleArrayListTest extends TestCase {
     list.addAll(asList(1D, 2D, 3D, 4D));
     Iterator<Double> iterator = list.iterator();
     assertEquals(4, list.size());
-    assertEquals(1D, (double) list.get(0));
-    assertEquals(1D, (double) iterator.next());
+    assertEquals(1D, (double) list.get(0), 0.0);
+    assertEquals(1D, (double) iterator.next(), 0.0);
     list.set(0, 1D);
-    assertEquals(2D, (double) iterator.next());
+    assertEquals(2D, (double) iterator.next(), 0.0);
 
     list.remove(0);
     try {
@@ -102,9 +102,9 @@ public class DoubleArrayListTest extends TestCase {
   }
 
   public void testGet() {
-    assertEquals(1D, (double) TERTIARY_LIST.get(0));
-    assertEquals(2D, (double) TERTIARY_LIST.get(1));
-    assertEquals(3D, (double) TERTIARY_LIST.get(2));
+    assertEquals(1D, (double) TERTIARY_LIST.get(0), 0.0);
+    assertEquals(2D, (double) TERTIARY_LIST.get(1), 0.0);
+    assertEquals(3D, (double) TERTIARY_LIST.get(2), 0.0);
 
     try {
       TERTIARY_LIST.get(-1);
@@ -122,9 +122,9 @@ public class DoubleArrayListTest extends TestCase {
   }
 
   public void testGetDouble() {
-    assertEquals(1D, TERTIARY_LIST.getDouble(0));
-    assertEquals(2D, TERTIARY_LIST.getDouble(1));
-    assertEquals(3D, TERTIARY_LIST.getDouble(2));
+    assertEquals(1D, TERTIARY_LIST.getDouble(0), 0.0);
+    assertEquals(2D, TERTIARY_LIST.getDouble(1), 0.0);
+    assertEquals(3D, TERTIARY_LIST.getDouble(2), 0.0);
 
     try {
       TERTIARY_LIST.get(-1);
@@ -163,11 +163,11 @@ public class DoubleArrayListTest extends TestCase {
     list.addDouble(2);
     list.addDouble(4);
 
-    assertEquals(2D, (double) list.set(0, 3D));
-    assertEquals(3D, list.getDouble(0));
+    assertEquals(2D, (double) list.set(0, 3D), 0.0);
+    assertEquals(3D, list.getDouble(0), 0.0);
 
-    assertEquals(4D, (double) list.set(1, 0D));
-    assertEquals(0D, list.getDouble(1));
+    assertEquals(4D, (double) list.set(1, 0D), 0.0);
+    assertEquals(0D, list.getDouble(1), 0.0);
 
     try {
       list.set(-1, 0D);
@@ -188,11 +188,11 @@ public class DoubleArrayListTest extends TestCase {
     list.addDouble(1);
     list.addDouble(3);
 
-    assertEquals(1D, list.setDouble(0, 0));
-    assertEquals(0D, list.getDouble(0));
+    assertEquals(1D, list.setDouble(0, 0), 0.0);
+    assertEquals(0D, list.getDouble(0), 0.0);
 
-    assertEquals(3D, list.setDouble(1, 0));
-    assertEquals(0D, list.getDouble(1));
+    assertEquals(3D, list.setDouble(1, 0), 0.0);
+    assertEquals(0D, list.getDouble(1), 0.0);
 
     try {
       list.setDouble(-1, 0);
@@ -257,8 +257,8 @@ public class DoubleArrayListTest extends TestCase {
 
     assertTrue(list.addAll(Collections.singleton(1D)));
     assertEquals(1, list.size());
-    assertEquals(1D, (double) list.get(0));
-    assertEquals(1D, list.getDouble(0));
+    assertEquals(1D, (double) list.get(0), 0.0);
+    assertEquals(1D, list.getDouble(0), 0.0);
 
     assertTrue(list.addAll(asList(2D, 3D, 4D, 5D, 6D)));
     assertEquals(asList(1D, 2D, 3D, 4D, 5D, 6D), list);
@@ -272,7 +272,7 @@ public class DoubleArrayListTest extends TestCase {
 
   public void testRemove() {
     list.addAll(TERTIARY_LIST);
-    assertEquals(1D, (double) list.remove(0));
+    assertEquals(1D, (double) list.remove(0), 0.0);
     assertEquals(asList(2D, 3D), list);
 
     assertTrue(list.remove(Double.valueOf(3)));
@@ -281,7 +281,7 @@ public class DoubleArrayListTest extends TestCase {
     assertFalse(list.remove(Double.valueOf(3)));
     assertEquals(asList(2D), list);
 
-    assertEquals(2D, (double) list.remove(0));
+    assertEquals(2D, (double) list.remove(0), 0.0);
     assertEquals(asList(), list);
 
     try {
@@ -299,20 +299,22 @@ public class DoubleArrayListTest extends TestCase {
   }
 
   public void testRemoveEndOfCapacity() {
-    DoubleList toRemove = DoubleArrayList.emptyList().mutableCopyWithCapacity(1);
+    DoubleList toRemove =
+        DoubleArrayList.emptyList().mutableCopyWithCapacity(1);
     toRemove.addDouble(3);
     toRemove.remove(0);
     assertEquals(0, toRemove.size());
   }
 
   public void testSublistRemoveEndOfCapacity() {
-    DoubleList toRemove = DoubleArrayList.emptyList().mutableCopyWithCapacity(1);
+    DoubleList toRemove =
+        DoubleArrayList.emptyList().mutableCopyWithCapacity(1);
     toRemove.addDouble(3);
     toRemove.subList(0, 1).clear();
     assertEquals(0, toRemove.size());
   }
 
-  private void assertImmutable(DoubleArrayList list) {
+  private void assertImmutable(DoubleList list) {
     if (list.contains(1D)) {
       throw new RuntimeException("Cannot test the immutability of lists that contain 1.");
     }
diff --git a/java/core/src/test/java/com/google/protobuf/DynamicMessageTest.java b/java/core/src/test/java/com/google/protobuf/DynamicMessageTest.java
index 77d14f6b..346c1e6a 100644
--- a/java/core/src/test/java/com/google/protobuf/DynamicMessageTest.java
+++ b/java/core/src/test/java/com/google/protobuf/DynamicMessageTest.java
@@ -51,8 +51,8 @@ public class DynamicMessageTest extends TestCase {
     new TestUtil.ReflectionTester(TestAllTypes.getDescriptor(), null);
 
   TestUtil.ReflectionTester extensionsReflectionTester =
-    new TestUtil.ReflectionTester(TestAllExtensions.getDescriptor(),
-                                  TestUtil.getExtensionRegistry());
+      new TestUtil.ReflectionTester(
+          TestAllExtensions.getDescriptor(), TestUtil.getFullExtensionRegistry());
   TestUtil.ReflectionTester packedReflectionTester =
     new TestUtil.ReflectionTester(TestPackedTypes.getDescriptor(), null);
 
@@ -194,9 +194,9 @@ public class DynamicMessageTest extends TestCase {
 
   public void testDynamicMessageExtensionParsing() throws Exception {
     ByteString rawBytes = TestUtil.getAllExtensionsSet().toByteString();
-    Message message = DynamicMessage.parseFrom(
-        TestAllExtensions.getDescriptor(), rawBytes,
-        TestUtil.getExtensionRegistry());
+    Message message =
+        DynamicMessage.parseFrom(
+            TestAllExtensions.getDescriptor(), rawBytes, TestUtil.getFullExtensionRegistry());
     extensionsReflectionTester.assertAllFieldsSetViaReflection(message);
 
     // Test Parser interface.
diff --git a/java/core/src/test/java/com/google/protobuf/FloatArrayListTest.java b/java/core/src/test/java/com/google/protobuf/FloatArrayListTest.java
index 903a79db..38eccc93 100644
--- a/java/core/src/test/java/com/google/protobuf/FloatArrayListTest.java
+++ b/java/core/src/test/java/com/google/protobuf/FloatArrayListTest.java
@@ -78,10 +78,10 @@ public class FloatArrayListTest extends TestCase {
     list.addAll(asList(1F, 2F, 3F, 4F));
     Iterator<Float> iterator = list.iterator();
     assertEquals(4, list.size());
-    assertEquals(1F, (float) list.get(0));
-    assertEquals(1F, (float) iterator.next());
+    assertEquals(1F, (float) list.get(0), 0.0f);
+    assertEquals(1F, (float) iterator.next(), 0.0f);
     list.set(0, 1F);
-    assertEquals(2F, (float) iterator.next());
+    assertEquals(2F, (float) iterator.next(), 0.0f);
 
     list.remove(0);
     try {
@@ -102,9 +102,9 @@ public class FloatArrayListTest extends TestCase {
   }
 
   public void testGet() {
-    assertEquals(1F, (float) TERTIARY_LIST.get(0));
-    assertEquals(2F, (float) TERTIARY_LIST.get(1));
-    assertEquals(3F, (float) TERTIARY_LIST.get(2));
+    assertEquals(1F, (float) TERTIARY_LIST.get(0), 0.0f);
+    assertEquals(2F, (float) TERTIARY_LIST.get(1), 0.0f);
+    assertEquals(3F, (float) TERTIARY_LIST.get(2), 0.0f);
 
     try {
       TERTIARY_LIST.get(-1);
@@ -122,9 +122,9 @@ public class FloatArrayListTest extends TestCase {
   }
 
   public void testGetFloat() {
-    assertEquals(1F, TERTIARY_LIST.getFloat(0));
-    assertEquals(2F, TERTIARY_LIST.getFloat(1));
-    assertEquals(3F, TERTIARY_LIST.getFloat(2));
+    assertEquals(1F, TERTIARY_LIST.getFloat(0), 0.0f);
+    assertEquals(2F, TERTIARY_LIST.getFloat(1), 0.0f);
+    assertEquals(3F, TERTIARY_LIST.getFloat(2), 0.0f);
 
     try {
       TERTIARY_LIST.get(-1);
@@ -163,11 +163,11 @@ public class FloatArrayListTest extends TestCase {
     list.addFloat(2);
     list.addFloat(4);
 
-    assertEquals(2F, (float) list.set(0, 3F));
-    assertEquals(3F, list.getFloat(0));
+    assertEquals(2F, (float) list.set(0, 3F), 0.0f);
+    assertEquals(3F, list.getFloat(0), 0.0f);
 
-    assertEquals(4F, (float) list.set(1, 0F));
-    assertEquals(0F, list.getFloat(1));
+    assertEquals(4F, (float) list.set(1, 0F), 0.0f);
+    assertEquals(0F, list.getFloat(1), 0.0f);
 
     try {
       list.set(-1, 0F);
@@ -188,11 +188,11 @@ public class FloatArrayListTest extends TestCase {
     list.addFloat(1);
     list.addFloat(3);
 
-    assertEquals(1F, list.setFloat(0, 0));
-    assertEquals(0F, list.getFloat(0));
+    assertEquals(1F, list.setFloat(0, 0), 0.0f);
+    assertEquals(0F, list.getFloat(0), 0.0f);
 
-    assertEquals(3F, list.setFloat(1, 0));
-    assertEquals(0F, list.getFloat(1));
+    assertEquals(3F, list.setFloat(1, 0), 0.0f);
+    assertEquals(0F, list.getFloat(1), 0.0f);
 
     try {
       list.setFloat(-1, 0);
@@ -257,8 +257,8 @@ public class FloatArrayListTest extends TestCase {
 
     assertTrue(list.addAll(Collections.singleton(1F)));
     assertEquals(1, list.size());
-    assertEquals(1F, (float) list.get(0));
-    assertEquals(1F, list.getFloat(0));
+    assertEquals(1F, (float) list.get(0), 0.0f);
+    assertEquals(1F, list.getFloat(0), 0.0f);
 
     assertTrue(list.addAll(asList(2F, 3F, 4F, 5F, 6F)));
     assertEquals(asList(1F, 2F, 3F, 4F, 5F, 6F), list);
@@ -272,7 +272,7 @@ public class FloatArrayListTest extends TestCase {
 
   public void testRemove() {
     list.addAll(TERTIARY_LIST);
-    assertEquals(1F, (float) list.remove(0));
+    assertEquals(1F, (float) list.remove(0), 0.0f);
     assertEquals(asList(2F, 3F), list);
 
     assertTrue(list.remove(Float.valueOf(3)));
@@ -281,7 +281,7 @@ public class FloatArrayListTest extends TestCase {
     assertFalse(list.remove(Float.valueOf(3)));
     assertEquals(asList(2F), list);
 
-    assertEquals(2F, (float) list.remove(0));
+    assertEquals(2F, (float) list.remove(0), 0.0f);
     assertEquals(asList(), list);
 
     try {
@@ -299,20 +299,22 @@ public class FloatArrayListTest extends TestCase {
   }
 
   public void testRemoveEndOfCapacity() {
-    FloatList toRemove = FloatArrayList.emptyList().mutableCopyWithCapacity(1);
+    FloatList toRemove =
+        FloatArrayList.emptyList().mutableCopyWithCapacity(1);
     toRemove.addFloat(3);
     toRemove.remove(0);
     assertEquals(0, toRemove.size());
   }
 
   public void testSublistRemoveEndOfCapacity() {
-    FloatList toRemove = FloatArrayList.emptyList().mutableCopyWithCapacity(1);
+    FloatList toRemove =
+        FloatArrayList.emptyList().mutableCopyWithCapacity(1);
     toRemove.addFloat(3);
     toRemove.subList(0, 1).clear();
     assertEquals(0, toRemove.size());
   }
 
-  private void assertImmutable(FloatArrayList list) {
+  private void assertImmutable(FloatList list) {
     if (list.contains(1F)) {
       throw new RuntimeException("Cannot test the immutability of lists that contain 1.");
     }
diff --git a/java/core/src/test/java/com/google/protobuf/GeneratedMessageTest.java b/java/core/src/test/java/com/google/protobuf/GeneratedMessageTest.java
index c9ebe7f5..a4143cd4 100644
--- a/java/core/src/test/java/com/google/protobuf/GeneratedMessageTest.java
+++ b/java/core/src/test/java/com/google/protobuf/GeneratedMessageTest.java
@@ -590,8 +590,8 @@ public class GeneratedMessageTest extends TestCase {
   // Extensions.
 
   TestUtil.ReflectionTester extensionsReflectionTester =
-    new TestUtil.ReflectionTester(TestAllExtensions.getDescriptor(),
-                                  TestUtil.getExtensionRegistry());
+      new TestUtil.ReflectionTester(
+          TestAllExtensions.getDescriptor(), TestUtil.getFullExtensionRegistry());
 
   public void testExtensionMessageOrBuilder() throws Exception {
     TestAllExtensions.Builder builder = TestAllExtensions.newBuilder();
diff --git a/java/core/src/test/java/com/google/protobuf/IntArrayListTest.java b/java/core/src/test/java/com/google/protobuf/IntArrayListTest.java
index d8e97d4f..9edc4344 100644
--- a/java/core/src/test/java/com/google/protobuf/IntArrayListTest.java
+++ b/java/core/src/test/java/com/google/protobuf/IntArrayListTest.java
@@ -299,20 +299,22 @@ public class IntArrayListTest extends TestCase {
   }
 
   public void testRemoveEndOfCapacity() {
-    IntList toRemove = IntArrayList.emptyList().mutableCopyWithCapacity(1);
+    IntList toRemove =
+        IntArrayList.emptyList().mutableCopyWithCapacity(1);
     toRemove.addInt(3);
     toRemove.remove(0);
     assertEquals(0, toRemove.size());
   }
 
   public void testSublistRemoveEndOfCapacity() {
-    IntList toRemove = IntArrayList.emptyList().mutableCopyWithCapacity(1);
+    IntList toRemove =
+        IntArrayList.emptyList().mutableCopyWithCapacity(1);
     toRemove.addInt(3);
     toRemove.subList(0, 1).clear();
     assertEquals(0, toRemove.size());
   }
 
-  private void assertImmutable(IntArrayList list) {
+  private void assertImmutable(IntList list) {
     if (list.contains(1)) {
       throw new RuntimeException("Cannot test the immutability of lists that contain 1.");
     }
diff --git a/java/core/src/test/java/com/google/protobuf/LiteTest.java b/java/core/src/test/java/com/google/protobuf/LiteTest.java
index 5ab80ca2..b20114e0 100644
--- a/java/core/src/test/java/com/google/protobuf/LiteTest.java
+++ b/java/core/src/test/java/com/google/protobuf/LiteTest.java
@@ -57,6 +57,8 @@ import protobuf_unittest.lite_equals_and_hash.LiteEqualsAndHash.TestOneofEquals;
 import protobuf_unittest.lite_equals_and_hash.LiteEqualsAndHash.TestRecursiveOneof;
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
 import java.lang.reflect.Field;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
@@ -2378,4 +2380,63 @@ public class LiteTest extends TestCase {
     } catch (NullPointerException expected) {
     }
   }
+
+  public void testSerializeToOutputStreamThrowsIOException() {
+    try {
+      TestAllTypesLite.newBuilder()
+          .setOptionalBytes(ByteString.copyFromUtf8("hello"))
+          .build()
+          .writeTo(
+              new OutputStream() {
+
+                @Override
+                public void write(int b) throws IOException {
+                  throw new IOException();
+                }
+              });
+      fail();
+    } catch (IOException expected) {
+    }
+  }
+
+  public void testUnpairedSurrogatesReplacedByQuestionMark() throws InvalidProtocolBufferException {
+    String testString = "foo \ud83d bar";
+    String expectedString = "foo ? bar";
+
+    TestAllTypesLite testMessage =
+        TestAllTypesLite.newBuilder().setOptionalString(testString).build();
+    ByteString serializedMessage = testMessage.toByteString();
+
+    // Behavior is compatible with String.getBytes("UTF-8"), which replaces
+    // unpaired surrogates with a question mark.
+    TestAllTypesLite parsedMessage = TestAllTypesLite.parseFrom(serializedMessage);
+    assertEquals(expectedString, parsedMessage.getOptionalString());
+
+    // Conversion happens during serialization.
+    ByteString expectedBytes = ByteString.copyFromUtf8(expectedString);
+    assertTrue(
+        String.format(
+            "Expected serializedMessage (%s) to contain \"%s\" (%s).",
+            encodeHex(serializedMessage), expectedString, encodeHex(expectedBytes)),
+        contains(serializedMessage, expectedBytes));
+  }
+
+  private String encodeHex(ByteString bytes) {
+    String hexDigits = "0123456789abcdef";
+    StringBuilder stringBuilder = new StringBuilder(bytes.size() * 2);
+    for (byte b : bytes) {
+      stringBuilder.append(hexDigits.charAt((b & 0xf0) >> 4));
+      stringBuilder.append(hexDigits.charAt(b & 0x0f));
+    }
+    return stringBuilder.toString();
+  }
+
+  private boolean contains(ByteString a, ByteString b) {
+    for (int i = 0; i <= a.size() - b.size(); ++i) {
+      if (a.substring(i, i + b.size()).equals(b)) {
+        return true;
+      }
+    }
+    return false;
+  }
 }
diff --git a/java/core/src/test/java/com/google/protobuf/LongArrayListTest.java b/java/core/src/test/java/com/google/protobuf/LongArrayListTest.java
index e50c7d1e..14a8e159 100644
--- a/java/core/src/test/java/com/google/protobuf/LongArrayListTest.java
+++ b/java/core/src/test/java/com/google/protobuf/LongArrayListTest.java
@@ -299,20 +299,22 @@ public class LongArrayListTest extends TestCase {
   }
 
   public void testRemoveEndOfCapacity() {
-    LongList toRemove = LongArrayList.emptyList().mutableCopyWithCapacity(1);
+    LongList toRemove =
+        LongArrayList.emptyList().mutableCopyWithCapacity(1);
     toRemove.addLong(3);
     toRemove.remove(0);
     assertEquals(0, toRemove.size());
   }
 
   public void testSublistRemoveEndOfCapacity() {
-    LongList toRemove = LongArrayList.emptyList().mutableCopyWithCapacity(1);
+    LongList toRemove =
+        LongArrayList.emptyList().mutableCopyWithCapacity(1);
     toRemove.addLong(3);
     toRemove.subList(0, 1).clear();
     assertEquals(0, toRemove.size());
   }
 
-  private void assertImmutable(LongArrayList list) {
+  private void assertImmutable(LongList list) {
     if (list.contains(1L)) {
       throw new RuntimeException("Cannot test the immutability of lists that contain 1.");
     }
diff --git a/java/core/src/test/java/com/google/protobuf/ProtobufArrayListTest.java b/java/core/src/test/java/com/google/protobuf/ProtobufArrayListTest.java
index af717bfd..0a2c3e37 100644
--- a/java/core/src/test/java/com/google/protobuf/ProtobufArrayListTest.java
+++ b/java/core/src/test/java/com/google/protobuf/ProtobufArrayListTest.java
@@ -42,33 +42,33 @@ import junit.framework.TestCase;
  * Tests for {@link ProtobufArrayList}.
  */
 public class ProtobufArrayListTest extends TestCase {
-  
+
   private static final ProtobufArrayList<Integer> UNARY_LIST = newImmutableProtoArrayList(1);
   private static final ProtobufArrayList<Integer> TERTIARY_LIST =
       newImmutableProtoArrayList(1, 2, 3);
-  
+
   private ProtobufArrayList<Integer> list;
-  
+
   @Override
   protected void setUp() throws Exception {
     list = new ProtobufArrayList<Integer>();
   }
-  
+
   public void testEmptyListReturnsSameInstance() {
     assertSame(ProtobufArrayList.emptyList(), ProtobufArrayList.emptyList());
   }
-  
+
   public void testEmptyListIsImmutable() {
     assertImmutable(ProtobufArrayList.<Integer>emptyList());
   }
-  
+
   public void testModificationWithIteration() {
     list.addAll(asList(1, 2, 3, 4));
     Iterator<Integer> iterator = list.iterator();
     assertEquals(4, list.size());
     assertEquals(1, (int) list.get(0));
     assertEquals(1, (int) iterator.next());
-    
+
     list.remove(0);
     try {
       iterator.next();
@@ -76,7 +76,7 @@ public class ProtobufArrayListTest extends TestCase {
     } catch (ConcurrentModificationException e) {
       // expected
     }
-    
+
     iterator = list.iterator();
     list.set(0, 1);
     try {
@@ -85,7 +85,7 @@ public class ProtobufArrayListTest extends TestCase {
     } catch (ConcurrentModificationException e) {
       // expected
     }
-    
+
     iterator = list.iterator();
     list.add(0, 0);
     try {
@@ -95,7 +95,7 @@ public class ProtobufArrayListTest extends TestCase {
       // expected
     }
   }
-  
+
   public void testMakeImmutable() {
     list.add(2);
     list.add(4);
@@ -104,107 +104,213 @@ public class ProtobufArrayListTest extends TestCase {
     list.makeImmutable();
     assertImmutable(list);
   }
-  
+
   public void testRemove() {
-    list.add(2);
-    list.add(4);
-    list.add(6);
+    list.addAll(TERTIARY_LIST);
+    assertEquals(1, (int) list.remove(0));
+    assertEquals(asList(2, 3), list);
 
-    list.remove(1);
-    assertEquals(asList(2, 6), list);
+    assertTrue(list.remove(Integer.valueOf(3)));
+    assertEquals(asList(2), list);
 
-    list.remove(1);
+    assertFalse(list.remove(Integer.valueOf(3)));
     assertEquals(asList(2), list);
 
-    list.remove(0);
+    assertEquals(2, (int) list.remove(0));
     assertEquals(asList(), list);
+
+    try {
+      list.remove(-1);
+      fail();
+    } catch (IndexOutOfBoundsException e) {
+      // expected
+    }
+
+    try {
+      list.remove(0);
+    } catch (IndexOutOfBoundsException e) {
+      // expected
+    }
   }
-  
+
   public void testGet() {
-    list.add(2);
-    list.add(6);
-    
-    assertEquals(2, (int) list.get(0));
-    assertEquals(6, (int) list.get(1));
+    assertEquals(1, (int) TERTIARY_LIST.get(0));
+    assertEquals(2, (int) TERTIARY_LIST.get(1));
+    assertEquals(3, (int) TERTIARY_LIST.get(2));
+
+    try {
+      TERTIARY_LIST.get(-1);
+      fail();
+    } catch (IndexOutOfBoundsException e) {
+      // expected
+    }
+
+    try {
+      TERTIARY_LIST.get(3);
+      fail();
+    } catch (IndexOutOfBoundsException e) {
+      // expected
+    }
   }
-  
+
   public void testSet() {
     list.add(2);
-    list.add(6);
-    
-    list.set(0, 1);
+    list.add(4);
+
+    assertEquals(2, (int) list.set(0, 3));
+    assertEquals(3, (int) list.get(0));
+
+    assertEquals(4, (int) list.set(1, 0));
+    assertEquals(0, (int) list.get(1));
+
+    try {
+      list.set(-1, 0);
+      fail();
+    } catch (IndexOutOfBoundsException e) {
+      // expected
+    }
+
+    try {
+      list.set(2, 0);
+      fail();
+    } catch (IndexOutOfBoundsException e) {
+      // expected
+    }
+  }
+
+  public void testAdd() {
+    assertEquals(0, list.size());
+
+    assertTrue(list.add(2));
+    assertEquals(asList(2), list);
+
+    assertTrue(list.add(3));
+    list.add(0, 4);
+    assertEquals(asList(4, 2, 3), list);
+
+    list.add(0, 1);
+    list.add(0, 0);
+    // Force a resize by getting up to 11 elements.
+    for (int i = 0; i < 6; i++) {
+      list.add(Integer.valueOf(5 + i));
+    }
+    assertEquals(asList(0, 1, 4, 2, 3, 5, 6, 7, 8, 9, 10), list);
+
+    try {
+      list.add(-1, 5);
+    } catch (IndexOutOfBoundsException e) {
+      // expected
+    }
+
+    try {
+      list.add(4, 5);
+    } catch (IndexOutOfBoundsException e) {
+      // expected
+    }
+  }
+
+  public void testAddAll() {
+    assertEquals(0, list.size());
+
+    assertTrue(list.addAll(Collections.singleton(1)));
+    assertEquals(1, list.size());
     assertEquals(1, (int) list.get(0));
-    list.set(1, 2);
-    assertEquals(2, (int) list.get(1));
+
+    assertTrue(list.addAll(asList(2, 3, 4, 5, 6)));
+    assertEquals(asList(1, 2, 3, 4, 5, 6), list);
+
+    assertTrue(list.addAll(TERTIARY_LIST));
+    assertEquals(asList(1, 2, 3, 4, 5, 6, 1, 2, 3), list);
+
+    assertFalse(list.addAll(Collections.<Integer>emptyList()));
+    assertFalse(list.addAll(IntArrayList.emptyList()));
+  }
+
+  public void testSize() {
+    assertEquals(0, ProtobufArrayList.emptyList().size());
+    assertEquals(1, UNARY_LIST.size());
+    assertEquals(3, TERTIARY_LIST.size());
+
+    list.add(3);
+    list.add(4);
+    list.add(6);
+    list.add(8);
+    assertEquals(4, list.size());
+
+    list.remove(0);
+    assertEquals(3, list.size());
+
+    list.add(17);
+    assertEquals(4, list.size());
   }
 
   private void assertImmutable(List<Integer> list) {
     if (list.contains(1)) {
       throw new RuntimeException("Cannot test the immutability of lists that contain 1.");
     }
-    
+
     try {
       list.add(1);
       fail();
     } catch (UnsupportedOperationException e) {
       // expected
     }
-    
+
     try {
       list.add(0, 1);
       fail();
     } catch (UnsupportedOperationException e) {
       // expected
     }
-    
+
     try {
       list.addAll(Collections.<Integer>emptyList());
       fail();
     } catch (UnsupportedOperationException e) {
       // expected
     }
-    
+
     try {
       list.addAll(Collections.singletonList(1));
       fail();
     } catch (UnsupportedOperationException e) {
       // expected
     }
-    
+
     try {
       list.addAll(new ProtobufArrayList<Integer>());
       fail();
     } catch (UnsupportedOperationException e) {
       // expected
     }
-    
+
     try {
       list.addAll(UNARY_LIST);
       fail();
     } catch (UnsupportedOperationException e) {
       // expected
     }
-    
+
     try {
       list.addAll(0, Collections.singleton(1));
       fail();
     } catch (UnsupportedOperationException e) {
       // expected
     }
-    
+
     try {
       list.addAll(0, UNARY_LIST);
       fail();
     } catch (UnsupportedOperationException e) {
       // expected
     }
-    
+
     try {
       list.addAll(0, Collections.<Integer>emptyList());
       fail();
     } catch (UnsupportedOperationException e) {
       // expected
-    } 
+    }
 
     try {
       list.clear();
@@ -219,56 +325,56 @@ public class ProtobufArrayListTest extends TestCase {
     } catch (UnsupportedOperationException e) {
       // expected
     }
-    
+
     try {
       list.remove(new Object());
       fail();
     } catch (UnsupportedOperationException e) {
       // expected
     }
-    
+
     try {
       list.removeAll(Collections.emptyList());
       fail();
     } catch (UnsupportedOperationException e) {
       // expected
     }
-    
+
     try {
       list.removeAll(Collections.singleton(1));
       fail();
     } catch (UnsupportedOperationException e) {
       // expected
     }
-    
+
     try {
       list.removeAll(UNARY_LIST);
       fail();
     } catch (UnsupportedOperationException e) {
       // expected
     }
-    
+
     try {
       list.retainAll(Collections.emptyList());
       fail();
     } catch (UnsupportedOperationException e) {
       // expected
     }
-    
+
     try {
       list.retainAll(Collections.singleton(1));
       fail();
     } catch (UnsupportedOperationException e) {
       // expected
     }
-    
+
     try {
       list.retainAll(UNARY_LIST);
       fail();
     } catch (UnsupportedOperationException e) {
       // expected
     }
-    
+
     try {
       list.set(0, 0);
       fail();
@@ -276,7 +382,7 @@ public class ProtobufArrayListTest extends TestCase {
       // expected
     }
   }
-  
+
   private static ProtobufArrayList<Integer> newImmutableProtoArrayList(int... elements) {
     ProtobufArrayList<Integer> list = new ProtobufArrayList<Integer>();
     for (int element : elements) {
diff --git a/java/core/src/test/java/com/google/protobuf/TestUtil.java b/java/core/src/test/java/com/google/protobuf/TestUtil.java
index b4bc3a3d..8ec22d3f 100644
--- a/java/core/src/test/java/com/google/protobuf/TestUtil.java
+++ b/java/core/src/test/java/com/google/protobuf/TestUtil.java
@@ -130,8 +130,6 @@ import static protobuf_unittest.UnittestProto.defaultFixed64Extension;
 import static protobuf_unittest.UnittestProto.defaultFloatExtension;
 import static protobuf_unittest.UnittestProto.defaultForeignEnumExtension;
 import static protobuf_unittest.UnittestProto.defaultImportEnumExtension;
-// The static imports are to avoid 100+ char lines.  The following is roughly equivalent to
-// import static protobuf_unittest.UnittestProto.*;
 import static protobuf_unittest.UnittestProto.defaultInt32Extension;
 import static protobuf_unittest.UnittestProto.defaultInt64Extension;
 import static protobuf_unittest.UnittestProto.defaultNestedEnumExtension;
@@ -263,12 +261,14 @@ public final class TestUtil {
     return ByteString.copyFrom(str.getBytes(Internal.UTF_8));
   }
 
+  // BEGIN FULL-RUNTIME
   /**
    * Dirties the message by resetting the momoized serialized size.
    */
   public static void resetMemoizedSize(AbstractMessage message) {
     message.memoizedSize = -1;
   }
+  // END FULL-RUNTIME
 
   /**
    * Get a {@code TestAllTypes} with all fields set as they would be by
@@ -1201,17 +1201,29 @@ public final class TestUtil {
    * Get an unmodifiable {@link ExtensionRegistry} containing all the
    * extensions of {@code TestAllExtensions}.
    */
-  public static ExtensionRegistry getExtensionRegistry() {
+  public static ExtensionRegistryLite getExtensionRegistry() {
+    ExtensionRegistryLite registry = ExtensionRegistryLite.newInstance();
+    registerAllExtensions(registry);
+    return registry.getUnmodifiable();
+  }
+
+  // BEGIN FULL-RUNTIME
+  /**
+   * Get an unmodifiable {@link ExtensionRegistry} containing all the
+   * extensions of {@code TestAllExtensions}.
+   */
+  public static ExtensionRegistry getFullExtensionRegistry() {
     ExtensionRegistry registry = ExtensionRegistry.newInstance();
     registerAllExtensions(registry);
     return registry.getUnmodifiable();
   }
+  // END FULL-RUNTIME
 
   /**
    * Register all of {@code TestAllExtensions}'s extensions with the
    * given {@link ExtensionRegistry}.
    */
-  public static void registerAllExtensions(ExtensionRegistry registry) {
+  public static void registerAllExtensions(ExtensionRegistryLite registry) {
     UnittestProto.registerAllExtensions(registry);
     TestUtilLite.registerAllExtensionsLite(registry);
   }
@@ -2634,6 +2646,7 @@ public final class TestUtil {
   }
 
   // =================================================================
+  // BEGIN FULL-RUNTIME
 
   /**
    * Performs the same things that the methods of {@code TestUtil} do, but
@@ -3819,6 +3832,16 @@ public final class TestUtil {
         "Couldn't read file: " + fullPath.getPath(), e);
     }
   }
+  // END FULL-RUNTIME
+
+  private static ByteString readBytesFromResource(String name) {
+    try {
+      return ByteString.copyFrom(
+          com.google.common.io.ByteStreams.toByteArray(TestUtil.class.getResourceAsStream(name)));
+    } catch (IOException e) {
+      throw new RuntimeException(e);
+    }
+  }
 
   /**
    * Get the bytes of the "golden message".  This is a serialized TestAllTypes
@@ -3829,7 +3852,7 @@ public final class TestUtil {
    */
   public static ByteString getGoldenMessage() {
     if (goldenMessage == null) {
-      goldenMessage = readBytesFromFile("golden_message_oneof_implemented");
+      goldenMessage = readBytesFromResource("/google/protobuf/testdata/golden_message_oneof_implemented");
     }
     return goldenMessage;
   }
@@ -3846,12 +3869,13 @@ public final class TestUtil {
   public static ByteString getGoldenPackedFieldsMessage() {
     if (goldenPackedFieldsMessage == null) {
       goldenPackedFieldsMessage =
-          readBytesFromFile("golden_packed_fields_message");
+          readBytesFromResource("/google/protobuf/testdata/golden_packed_fields_message");
     }
     return goldenPackedFieldsMessage;
   }
   private static ByteString goldenPackedFieldsMessage = null;
 
+  // BEGIN FULL-RUNTIME
   /**
    * Mock implementation of {@link GeneratedMessage.BuilderParent} for testing.
    *
@@ -3871,4 +3895,5 @@ public final class TestUtil {
       return invalidations;
     }
   }
+  // END FULL-RUNTIME
 }
diff --git a/java/core/src/test/java/com/google/protobuf/TextFormatTest.java b/java/core/src/test/java/com/google/protobuf/TextFormatTest.java
index 720061d2..24d5589f 100644
--- a/java/core/src/test/java/com/google/protobuf/TextFormatTest.java
+++ b/java/core/src/test/java/com/google/protobuf/TextFormatTest.java
@@ -382,17 +382,14 @@ public class TextFormatTest extends TestCase {
 
   public void testMergeExtensions() throws Exception {
     TestAllExtensions.Builder builder = TestAllExtensions.newBuilder();
-    TextFormat.merge(allExtensionsSetText,
-                     TestUtil.getExtensionRegistry(),
-                     builder);
+    TextFormat.merge(allExtensionsSetText, TestUtil.getFullExtensionRegistry(), builder);
     TestUtil.assertAllExtensionsSet(builder.build());
   }
 
   public void testParseExtensions() throws Exception {
     TestUtil.assertAllExtensionsSet(
-        TextFormat.parse(allExtensionsSetText,
-                         TestUtil.getExtensionRegistry(),
-                         TestAllExtensions.class));
+        TextFormat.parse(
+            allExtensionsSetText, TestUtil.getFullExtensionRegistry(), TestAllExtensions.class));
   }
 
   public void testMergeAndParseCompatibility() throws Exception {
@@ -523,7 +520,7 @@ public class TextFormatTest extends TestCase {
     // Test merge().
     TestAllTypes.Builder builder = TestAllTypes.newBuilder();
     try {
-      TextFormat.merge(text, TestUtil.getExtensionRegistry(), builder);
+      TextFormat.merge(text, TestUtil.getFullExtensionRegistry(), builder);
       fail("Expected parse exception.");
     } catch (TextFormat.ParseException e) {
       assertEquals(error, e.getMessage());
@@ -531,8 +528,7 @@ public class TextFormatTest extends TestCase {
 
     // Test parse().
     try {
-      TextFormat.parse(
-          text, TestUtil.getExtensionRegistry(), TestAllTypes.class);
+      TextFormat.parse(text, TestUtil.getFullExtensionRegistry(), TestAllTypes.class);
       fail("Expected parse exception.");
     } catch (TextFormat.ParseException e) {
       assertEquals(error, e.getMessage());
@@ -544,8 +540,7 @@ public class TextFormatTest extends TestCase {
       String text) {
     TestAllTypes.Builder builder = TestAllTypes.newBuilder();
     try {
-      parserWithOverwriteForbidden.merge(
-          text, TestUtil.getExtensionRegistry(), builder);
+      parserWithOverwriteForbidden.merge(text, TestUtil.getFullExtensionRegistry(), builder);
       fail("Expected parse exception.");
     } catch (TextFormat.ParseException e) {
       assertEquals(error, e.getMessage());
@@ -555,8 +550,7 @@ public class TextFormatTest extends TestCase {
   private TestAllTypes assertParseSuccessWithOverwriteForbidden(
       String text) throws TextFormat.ParseException {
     TestAllTypes.Builder builder = TestAllTypes.newBuilder();
-    parserWithOverwriteForbidden.merge(
-        text, TestUtil.getExtensionRegistry(), builder);
+    parserWithOverwriteForbidden.merge(text, TestUtil.getFullExtensionRegistry(), builder);
     return builder.build();
   }
 
@@ -1118,8 +1112,7 @@ public class TextFormatTest extends TestCase {
     String input = "foo_string: \"stringvalue\" foo_int: 123";
     TestOneof2.Builder builder = TestOneof2.newBuilder();
     try {
-      parserWithOverwriteForbidden.merge(
-          input, TestUtil.getExtensionRegistry(), builder);
+      parserWithOverwriteForbidden.merge(input, TestUtil.getFullExtensionRegistry(), builder);
       fail("Expected parse exception.");
     } catch (TextFormat.ParseException e) {
       assertEquals("1:36: Field \"protobuf_unittest.TestOneof2.foo_int\""
@@ -1131,7 +1124,7 @@ public class TextFormatTest extends TestCase {
   public void testOneofOverwriteAllowed() throws Exception {
     String input = "foo_string: \"stringvalue\" foo_int: 123";
     TestOneof2.Builder builder = TestOneof2.newBuilder();
-    defaultParser.merge(input, TestUtil.getExtensionRegistry(), builder);
+    defaultParser.merge(input, TestUtil.getFullExtensionRegistry(), builder);
     // Only the last value sticks.
     TestOneof2 oneof = builder.build();
     assertFalse(oneof.hasFooString());
diff --git a/java/core/src/test/java/com/google/protobuf/WireFormatTest.java b/java/core/src/test/java/com/google/protobuf/WireFormatTest.java
index 03c33ecf..425b56da 100644
--- a/java/core/src/test/java/com/google/protobuf/WireFormatTest.java
+++ b/java/core/src/test/java/com/google/protobuf/WireFormatTest.java
@@ -132,7 +132,7 @@ public class WireFormatTest extends TestCase {
     TestAllTypes message = TestUtil.getAllSet();
     ByteString rawBytes = message.toByteString();
 
-    ExtensionRegistry registry = TestUtil.getExtensionRegistry();
+    ExtensionRegistryLite registry = TestUtil.getExtensionRegistry();
 
     TestAllExtensions message2 =
       TestAllExtensions.parseFrom(rawBytes, registry);
@@ -145,7 +145,7 @@ public class WireFormatTest extends TestCase {
     TestPackedExtensions message = TestUtil.getPackedExtensionsSet();
     ByteString rawBytes = message.toByteString();
 
-    ExtensionRegistry registry = TestUtil.getExtensionRegistry();
+    ExtensionRegistryLite registry = TestUtil.getExtensionRegistry();
 
     TestPackedExtensions message2 =
         TestPackedExtensions.parseFrom(rawBytes, registry);
diff --git a/java/core/src/test/proto/com/google/protobuf/lazy_fields_lite.proto b/java/core/src/test/proto/com/google/protobuf/lazy_fields_lite.proto
index 5580f72d..736a344f 100644
--- a/java/core/src/test/proto/com/google/protobuf/lazy_fields_lite.proto
+++ b/java/core/src/test/proto/com/google/protobuf/lazy_fields_lite.proto
@@ -36,8 +36,6 @@ syntax = "proto2";
 
 package protobuf_unittest;
 
-option optimize_for = LITE_RUNTIME;
-
 message LazyMessageLite {
   optional int32 num = 1;
   optional int32 num_with_default = 2 [default = 421];
diff --git a/java/core/src/test/proto/com/google/protobuf/lite_equals_and_hash.proto b/java/core/src/test/proto/com/google/protobuf/lite_equals_and_hash.proto
index b18b0d79..20fa03b9 100644
--- a/java/core/src/test/proto/com/google/protobuf/lite_equals_and_hash.proto
+++ b/java/core/src/test/proto/com/google/protobuf/lite_equals_and_hash.proto
@@ -34,7 +34,6 @@ syntax = "proto2";
 
 package protobuf_unittest.lite_equals_and_hash;
 
-option optimize_for = LITE_RUNTIME;
 
 message TestOneofEquals {
   oneof oneof_field {
diff --git a/java/core/src/test/proto/com/google/protobuf/map_lite_test.proto b/java/core/src/test/proto/com/google/protobuf/map_lite_test.proto
index c04f5d57..bc2105e5 100644
--- a/java/core/src/test/proto/com/google/protobuf/map_lite_test.proto
+++ b/java/core/src/test/proto/com/google/protobuf/map_lite_test.proto
@@ -30,10 +30,9 @@
 
 syntax = "proto3";
 
-package map_lite_test;
+package map_test;
 
-option optimize_for = LITE_RUNTIME;
-option java_package = "map_lite_test";
+option java_package = "map_test";
 option java_outer_classname = "MapTestProto";
 
 message TestMap {
diff --git a/java/core/src/test/proto/com/google/protobuf/nested_extension_lite.proto b/java/core/src/test/proto/com/google/protobuf/nested_extension_lite.proto
index a95c38b2..6793d6b7 100644
--- a/java/core/src/test/proto/com/google/protobuf/nested_extension_lite.proto
+++ b/java/core/src/test/proto/com/google/protobuf/nested_extension_lite.proto
@@ -38,7 +38,6 @@ syntax = "proto2";
 
 package protobuf_unittest;
 
-option optimize_for = LITE_RUNTIME;
 
 import "com/google/protobuf/non_nested_extension_lite.proto";
 
diff --git a/java/core/src/test/proto/com/google/protobuf/non_nested_extension_lite.proto b/java/core/src/test/proto/com/google/protobuf/non_nested_extension_lite.proto
index 37c369ed..e42faaa8 100644
--- a/java/core/src/test/proto/com/google/protobuf/non_nested_extension_lite.proto
+++ b/java/core/src/test/proto/com/google/protobuf/non_nested_extension_lite.proto
@@ -36,7 +36,6 @@ syntax = "proto2";
 
 package protobuf_unittest;
 
-option optimize_for = LITE_RUNTIME;
 
 message MessageLiteToBeExtended {
   extensions 1 to max;
diff --git a/java/util/src/main/java/com/google/protobuf/util/Durations.java b/java/util/src/main/java/com/google/protobuf/util/Durations.java
index fb7f4343..17b41cbb 100644
--- a/java/util/src/main/java/com/google/protobuf/util/Durations.java
+++ b/java/util/src/main/java/com/google/protobuf/util/Durations.java
@@ -61,6 +61,9 @@ public final class Durations {
   public static final Duration MAX_VALUE =
       Duration.newBuilder().setSeconds(DURATION_SECONDS_MAX).setNanos(999999999).build();
 
+  /** A constant holding the duration of zero. */
+  public static final Duration ZERO = Duration.newBuilder().setSeconds(0L).setNanos(0).build();
+
   private Durations() {}
 
   private static final Comparator<Duration> COMPARATOR =
diff --git a/java/util/src/main/java/com/google/protobuf/util/FieldMaskTree.java b/java/util/src/main/java/com/google/protobuf/util/FieldMaskTree.java
index 4a13fb1d..7b4facc1 100644
--- a/java/util/src/main/java/com/google/protobuf/util/FieldMaskTree.java
+++ b/java/util/src/main/java/com/google/protobuf/util/FieldMaskTree.java
@@ -249,12 +249,9 @@ final class FieldMaskTree {
           continue;
         }
         String childPath = path.isEmpty() ? entry.getKey() : path + "." + entry.getKey();
-        merge(
-            entry.getValue(),
-            childPath,
-            (Message) source.getField(field),
-            destination.getFieldBuilder(field),
-            options);
+        Message.Builder childBuilder = ((Message) destination.getField(field)).toBuilder();
+        merge(entry.getValue(), childPath, (Message) source.getField(field), childBuilder, options);
+        destination.setField(field, childBuilder.buildPartial());
         continue;
       }
       if (field.isRepeated()) {
@@ -275,7 +272,12 @@ final class FieldMaskTree {
             }
           } else {
             if (source.hasField(field)) {
-              destination.getFieldBuilder(field).mergeFrom((Message) source.getField(field));
+              destination.setField(
+                  field,
+                  ((Message) destination.getField(field))
+                      .toBuilder()
+                      .mergeFrom((Message) source.getField(field))
+                      .build());
             }
           }
         } else {
diff --git a/java/util/src/main/java/com/google/protobuf/util/FieldMaskUtil.java b/java/util/src/main/java/com/google/protobuf/util/FieldMaskUtil.java
index b2f849c4..aedc5eac 100644
--- a/java/util/src/main/java/com/google/protobuf/util/FieldMaskUtil.java
+++ b/java/util/src/main/java/com/google/protobuf/util/FieldMaskUtil.java
@@ -235,7 +235,7 @@ public class FieldMaskUtil {
   /**
    * Converts a FieldMask to its canonical form. In the canonical form of a
    * FieldMask, all field paths are sorted alphabetically and redundant field
-   * paths are moved.
+   * paths are removed.
    */
   public static FieldMask normalize(FieldMask mask) {
     return new FieldMaskTree(mask).toFieldMask();
diff --git a/java/util/src/main/java/com/google/protobuf/util/JsonFormat.java b/java/util/src/main/java/com/google/protobuf/util/JsonFormat.java
index 7f69ee68..973f1517 100644
--- a/java/util/src/main/java/com/google/protobuf/util/JsonFormat.java
+++ b/java/util/src/main/java/com/google/protobuf/util/JsonFormat.java
@@ -610,7 +610,7 @@ public class JsonFormat {
     private final CharSequence blankOrNewLine;
 
     private static class GsonHolder {
-      private static final Gson DEFAULT_GSON = new GsonBuilder().disableHtmlEscaping().create();
+      private static final Gson DEFAULT_GSON = new GsonBuilder().create();
     }
 
     PrinterImpl(
diff --git a/java/util/src/test/java/com/google/protobuf/util/FieldMaskTreeTest.java b/java/util/src/test/java/com/google/protobuf/util/FieldMaskTreeTest.java
index 853b6151..a0d317d4 100644
--- a/java/util/src/test/java/com/google/protobuf/util/FieldMaskTreeTest.java
+++ b/java/util/src/test/java/com/google/protobuf/util/FieldMaskTreeTest.java
@@ -30,9 +30,14 @@
 
 package com.google.protobuf.util;
 
+import com.google.protobuf.DynamicMessage;
+import com.google.protobuf.Message;
+import com.google.protobuf.UninitializedMessageException;
 import protobuf_unittest.UnittestProto.NestedTestAllTypes;
 import protobuf_unittest.UnittestProto.TestAllTypes;
 import protobuf_unittest.UnittestProto.TestAllTypes.NestedMessage;
+import protobuf_unittest.UnittestProto.TestRequired;
+import protobuf_unittest.UnittestProto.TestRequiredMessage;
 import junit.framework.TestCase;
 
 public class FieldMaskTreeTest extends TestCase {
@@ -90,8 +95,68 @@ public class FieldMaskTreeTest extends TestCase {
     tree.intersectFieldPath("bar", result);
     assertEquals("bar.baz,bar.quz,foo", result.toString());
   }
-
+  
   public void testMerge() throws Exception {
+    testMergeImpl(true);
+    testMergeImpl(false);
+    testMergeRequire(false);
+    testMergeRequire(true);
+  }
+
+  private void merge(
+      FieldMaskTree tree,
+      Message source,
+      Message.Builder builder,
+      FieldMaskUtil.MergeOptions options,
+      boolean useDynamicMessage)
+      throws Exception {
+    if (useDynamicMessage) {
+      Message.Builder newBuilder =
+          DynamicMessage.newBuilder(source.getDescriptorForType())
+              .mergeFrom(builder.buildPartial().toByteArray());
+      tree.merge(
+          DynamicMessage.newBuilder(source.getDescriptorForType())
+              .mergeFrom(source.toByteArray())
+              .build(),
+          newBuilder,
+          options);
+      builder.clear();
+      builder.mergeFrom(newBuilder.buildPartial());
+    } else {
+      tree.merge(source, builder, options);
+    }
+  }
+
+  private void testMergeRequire(boolean useDynamicMessage) throws Exception {
+    TestRequired value = TestRequired.newBuilder().setA(4321).setB(8765).setC(233333).build();
+    TestRequiredMessage source = TestRequiredMessage.newBuilder().setRequiredMessage(value).build();
+
+    FieldMaskUtil.MergeOptions options = new FieldMaskUtil.MergeOptions();
+    TestRequiredMessage.Builder builder = TestRequiredMessage.newBuilder();
+    merge(
+        new FieldMaskTree().addFieldPath("required_message.a"),
+        source,
+        builder,
+        options,
+        useDynamicMessage);
+    assertTrue(builder.hasRequiredMessage());
+    assertTrue(builder.getRequiredMessage().hasA());
+    assertFalse(builder.getRequiredMessage().hasB());
+    assertFalse(builder.getRequiredMessage().hasC());
+    merge(
+        new FieldMaskTree().addFieldPath("required_message.b").addFieldPath("required_message.c"),
+        source,
+        builder,
+        options,
+        useDynamicMessage);
+    try {
+      assertEquals(builder.build(), source);
+    } catch (UninitializedMessageException e) {
+      throw new AssertionError("required field isn't set", e);
+    }
+  }
+
+  private void testMergeImpl(boolean useDynamicMessage) throws Exception {
     TestAllTypes value =
         TestAllTypes.newBuilder()
             .setOptionalInt32(1234)
@@ -119,45 +184,51 @@ public class FieldMaskTreeTest extends TestCase {
 
     // Test merging each individual field.
     NestedTestAllTypes.Builder builder = NestedTestAllTypes.newBuilder();
-    new FieldMaskTree().addFieldPath("payload.optional_int32").merge(source, builder, options);
+    merge(new FieldMaskTree().addFieldPath("payload.optional_int32"),
+        source, builder, options, useDynamicMessage);
     NestedTestAllTypes.Builder expected = NestedTestAllTypes.newBuilder();
     expected.getPayloadBuilder().setOptionalInt32(1234);
     assertEquals(expected.build(), builder.build());
 
     builder = NestedTestAllTypes.newBuilder();
-    new FieldMaskTree()
-        .addFieldPath("payload.optional_nested_message")
-        .merge(source, builder, options);
+    merge(new FieldMaskTree().addFieldPath("payload.optional_nested_message"),
+        source, builder, options, useDynamicMessage);
     expected = NestedTestAllTypes.newBuilder();
     expected.getPayloadBuilder().setOptionalNestedMessage(NestedMessage.newBuilder().setBb(5678));
     assertEquals(expected.build(), builder.build());
 
     builder = NestedTestAllTypes.newBuilder();
-    new FieldMaskTree().addFieldPath("payload.repeated_int32").merge(source, builder, options);
+    merge(new FieldMaskTree().addFieldPath("payload.repeated_int32"),
+        source, builder, options, useDynamicMessage);
     expected = NestedTestAllTypes.newBuilder();
     expected.getPayloadBuilder().addRepeatedInt32(4321);
     assertEquals(expected.build(), builder.build());
 
     builder = NestedTestAllTypes.newBuilder();
-    new FieldMaskTree()
-        .addFieldPath("payload.repeated_nested_message")
-        .merge(source, builder, options);
+    merge(new FieldMaskTree().addFieldPath("payload.repeated_nested_message"),
+        source, builder, options, useDynamicMessage);
     expected = NestedTestAllTypes.newBuilder();
     expected.getPayloadBuilder().addRepeatedNestedMessage(NestedMessage.newBuilder().setBb(8765));
     assertEquals(expected.build(), builder.build());
 
     builder = NestedTestAllTypes.newBuilder();
-    new FieldMaskTree()
-        .addFieldPath("child.payload.optional_int32")
-        .merge(source, builder, options);
+    merge(
+        new FieldMaskTree().addFieldPath("child.payload.optional_int32"),
+        source,
+        builder,
+        options,
+        useDynamicMessage);
     expected = NestedTestAllTypes.newBuilder();
     expected.getChildBuilder().getPayloadBuilder().setOptionalInt32(1234);
     assertEquals(expected.build(), builder.build());
 
     builder = NestedTestAllTypes.newBuilder();
-    new FieldMaskTree()
-        .addFieldPath("child.payload.optional_nested_message")
-        .merge(source, builder, options);
+    merge(
+        new FieldMaskTree().addFieldPath("child.payload.optional_nested_message"),
+        source,
+        builder,
+        options,
+        useDynamicMessage);
     expected = NestedTestAllTypes.newBuilder();
     expected
         .getChildBuilder()
@@ -166,17 +237,15 @@ public class FieldMaskTreeTest extends TestCase {
     assertEquals(expected.build(), builder.build());
 
     builder = NestedTestAllTypes.newBuilder();
-    new FieldMaskTree()
-        .addFieldPath("child.payload.repeated_int32")
-        .merge(source, builder, options);
+    merge(new FieldMaskTree().addFieldPath("child.payload.repeated_int32"),
+        source, builder, options, useDynamicMessage);
     expected = NestedTestAllTypes.newBuilder();
     expected.getChildBuilder().getPayloadBuilder().addRepeatedInt32(4321);
     assertEquals(expected.build(), builder.build());
 
     builder = NestedTestAllTypes.newBuilder();
-    new FieldMaskTree()
-        .addFieldPath("child.payload.repeated_nested_message")
-        .merge(source, builder, options);
+    merge(new FieldMaskTree().addFieldPath("child.payload.repeated_nested_message"),
+        source, builder, options, useDynamicMessage);
     expected = NestedTestAllTypes.newBuilder();
     expected
         .getChildBuilder()
@@ -186,23 +255,23 @@ public class FieldMaskTreeTest extends TestCase {
 
     // Test merging all fields.
     builder = NestedTestAllTypes.newBuilder();
-    new FieldMaskTree()
-        .addFieldPath("child")
-        .addFieldPath("payload")
-        .merge(source, builder, options);
+    merge(new FieldMaskTree().addFieldPath("child").addFieldPath("payload"),
+        source, builder, options, useDynamicMessage);
     assertEquals(source, builder.build());
 
     // Test repeated options.
     builder = NestedTestAllTypes.newBuilder();
     builder.getPayloadBuilder().addRepeatedInt32(1000);
-    new FieldMaskTree().addFieldPath("payload.repeated_int32").merge(source, builder, options);
+    merge(new FieldMaskTree().addFieldPath("payload.repeated_int32"),
+        source, builder, options, useDynamicMessage);
     // Default behavior is to append repeated fields.
     assertEquals(2, builder.getPayload().getRepeatedInt32Count());
     assertEquals(1000, builder.getPayload().getRepeatedInt32(0));
     assertEquals(4321, builder.getPayload().getRepeatedInt32(1));
     // Change to replace repeated fields.
     options.setReplaceRepeatedFields(true);
-    new FieldMaskTree().addFieldPath("payload.repeated_int32").merge(source, builder, options);
+    merge(new FieldMaskTree().addFieldPath("payload.repeated_int32"),
+        source, builder, options, useDynamicMessage);
     assertEquals(1, builder.getPayload().getRepeatedInt32Count());
     assertEquals(4321, builder.getPayload().getRepeatedInt32(0));
 
@@ -210,7 +279,8 @@ public class FieldMaskTreeTest extends TestCase {
     builder = NestedTestAllTypes.newBuilder();
     builder.getPayloadBuilder().setOptionalInt32(1000);
     builder.getPayloadBuilder().setOptionalUint32(2000);
-    new FieldMaskTree().addFieldPath("payload").merge(source, builder, options);
+    merge(new FieldMaskTree().addFieldPath("payload"),
+        source, builder, options, useDynamicMessage);
     // Default behavior is to merge message fields.
     assertEquals(1234, builder.getPayload().getOptionalInt32());
     assertEquals(2000, builder.getPayload().getOptionalUint32());
@@ -218,14 +288,14 @@ public class FieldMaskTreeTest extends TestCase {
     // Test merging unset message fields.
     NestedTestAllTypes clearedSource = source.toBuilder().clearPayload().build();
     builder = NestedTestAllTypes.newBuilder();
-    new FieldMaskTree().addFieldPath("payload").merge(clearedSource, builder, options);
+    merge(new FieldMaskTree().addFieldPath("payload"),
+        clearedSource, builder, options, useDynamicMessage);
     assertEquals(false, builder.hasPayload());
 
     // Skip a message field if they are unset in both source and target.
     builder = NestedTestAllTypes.newBuilder();
-    new FieldMaskTree()
-        .addFieldPath("payload.optional_int32")
-        .merge(clearedSource, builder, options);
+    merge(new FieldMaskTree().addFieldPath("payload.optional_int32"),
+        clearedSource, builder, options, useDynamicMessage);
     assertEquals(false, builder.hasPayload());
 
     // Change to replace message fields.
@@ -233,7 +303,8 @@ public class FieldMaskTreeTest extends TestCase {
     builder = NestedTestAllTypes.newBuilder();
     builder.getPayloadBuilder().setOptionalInt32(1000);
     builder.getPayloadBuilder().setOptionalUint32(2000);
-    new FieldMaskTree().addFieldPath("payload").merge(source, builder, options);
+    merge(new FieldMaskTree().addFieldPath("payload"),
+        source, builder, options, useDynamicMessage);
     assertEquals(1234, builder.getPayload().getOptionalInt32());
     assertEquals(0, builder.getPayload().getOptionalUint32());
 
@@ -241,7 +312,8 @@ public class FieldMaskTreeTest extends TestCase {
     builder = NestedTestAllTypes.newBuilder();
     builder.getPayloadBuilder().setOptionalInt32(1000);
     builder.getPayloadBuilder().setOptionalUint32(2000);
-    new FieldMaskTree().addFieldPath("payload").merge(clearedSource, builder, options);
+    merge(new FieldMaskTree().addFieldPath("payload"),
+        clearedSource, builder, options, useDynamicMessage);
     assertEquals(false, builder.hasPayload());
 
     // Test merging unset primitive fields.
@@ -249,18 +321,16 @@ public class FieldMaskTreeTest extends TestCase {
     builder.getPayloadBuilder().clearOptionalInt32();
     NestedTestAllTypes sourceWithPayloadInt32Unset = builder.build();
     builder = source.toBuilder();
-    new FieldMaskTree()
-        .addFieldPath("payload.optional_int32")
-        .merge(sourceWithPayloadInt32Unset, builder, options);
+    merge(new FieldMaskTree().addFieldPath("payload.optional_int32"),
+        sourceWithPayloadInt32Unset, builder, options, useDynamicMessage);
     assertEquals(true, builder.getPayload().hasOptionalInt32());
     assertEquals(0, builder.getPayload().getOptionalInt32());
 
     // Change to clear unset primitive fields.
     options.setReplacePrimitiveFields(true);
     builder = source.toBuilder();
-    new FieldMaskTree()
-        .addFieldPath("payload.optional_int32")
-        .merge(sourceWithPayloadInt32Unset, builder, options);
+    merge(new FieldMaskTree().addFieldPath("payload.optional_int32"),
+        sourceWithPayloadInt32Unset, builder, options, useDynamicMessage);
     assertEquals(true, builder.hasPayload());
     assertEquals(false, builder.getPayload().hasOptionalInt32());
   }
diff --git a/java/util/src/test/java/com/google/protobuf/util/JsonFormatTest.java b/java/util/src/test/java/com/google/protobuf/util/JsonFormatTest.java
index 6ef08508..d9bbe587 100644
--- a/java/util/src/test/java/com/google/protobuf/util/JsonFormatTest.java
+++ b/java/util/src/test/java/com/google/protobuf/util/JsonFormatTest.java
@@ -70,7 +70,6 @@ import java.io.StringReader;
 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.util.Collections;
-import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Locale;
 import java.util.Set;
@@ -1188,10 +1187,14 @@ public class JsonFormatTest extends TestCase {
     assertRoundTripEquals(message);
   }
 
-  public void testDefaultGsonDoesNotHtmlEscape() throws Exception {
-    TestAllTypes message = TestAllTypes.newBuilder().setOptionalString("=").build();
-    assertEquals(
-        "{\n" + "  \"optionalString\": \"=\"" + "\n}", JsonFormat.printer().print(message));
+  // Regression test for b/73832901. Make sure html tags are escaped.
+  public void testHtmlEscape() throws Exception {
+    TestAllTypes message = TestAllTypes.newBuilder().setOptionalString("</script>").build();
+    assertEquals("{\n  \"optionalString\": \"\\u003c/script\\u003e\"\n}", toJsonString(message));
+
+    TestAllTypes.Builder builder = TestAllTypes.newBuilder();
+    JsonFormat.parser().merge(toJsonString(message), builder);
+    assertEquals(message.getOptionalString(), builder.getOptionalString());
   }
 
   public void testIncludingDefaultValueFields() throws Exception {