More TODOs done.

- Removed a TODO without change in DescriptorPool.LookupSymbol - the TODOs were around performance, and this is only used during descriptor initialization
- Make the CodedInputStream limits read-only, adding a static factory method for the rare cases when this is useful
- Extracted IDeepCloneable into its own file.

1 files changed, 4 insertions, 3 deletions

diff --git a/csharp/src/Google.Protobuf/Reflection/DescriptorPool.cs b/csharp/src/Google.Protobuf/Reflection/DescriptorPool.cs
index 157ea400..759955e6 100644
--- a/csharp/src/Google.Protobuf/Reflection/DescriptorPool.cs
+++ b/csharp/src/Google.Protobuf/Reflection/DescriptorPool.cs
@@ -257,10 +257,12 @@ namespace Google.Protobuf.Reflection
         /// or unqualified. C++-like name lookup semantics are used to search for the
         /// matching descriptor.
         /// </summary>
+        /// <remarks>
+        /// This isn't heavily optimized, but it's only used during cross linking anyway.
+        /// If it starts being used more widely, we should look at performance more carefully.
+        /// </remarks>
         internal IDescriptor LookupSymbol(string name, IDescriptor relativeTo)
         {
-            // TODO(jonskeet):  This could be optimized in a number of ways.
-
             IDescriptor result;
             if (name.StartsWith("."))
             {
@@ -282,7 +284,6 @@ namespace Google.Protobuf.Reflection
                 {
                     // Chop off the last component of the scope.
 
-                    // TODO(jonskeet): Make this more efficient. May not be worth using StringBuilder at all
                     int dotpos = scopeToTry.ToString().LastIndexOf(".");
                     if (dotpos == -1)
                     {