[SPARK-17843][WEB UI] Indicate event logs pending for processing on history server UI

## What changes were proposed in this pull request?

History Server UI's application listing to display information on currently under process event logs so a user knows that pending this processing an application may not list on the UI.

When there are no event logs under process, the application list page has a "Last Updated" date-time at the top indicating the date-time of the last _completed_ scan of the event logs. The value is displayed to the user in his/her local time zone.
## How was this patch tested?

All unit tests pass. Particularly all the suites under org.apache.spark.deploy.history.\* were run to test changes.
- Very first startup - Pending logs - no logs processed yet:

<img width="1280" alt="screen shot 2016-10-24 at 3 07 04 pm" src="https://cloud.githubusercontent.com/assets/12079825/19640981/b8d2a96a-99fc-11e6-9b1f-2d736fe90e48.png">
- Very first startup - Pending logs - some logs processed:

<img width="1280" alt="screen shot 2016-10-24 at 3 18 42 pm" src="https://cloud.githubusercontent.com/assets/12079825/19641087/3f8e3bae-99fd-11e6-9ef1-e0e70d71d8ef.png">
- Last updated - No currently pending logs:

<img width="1280" alt="screen shot 2016-10-17 at 8 34 37 pm" src="https://cloud.githubusercontent.com/assets/12079825/19443100/4d13946c-94a9-11e6-8ee2-c442729bb206.png">
- Last updated - With some currently pending logs:

<img width="1280" alt="screen shot 2016-10-24 at 3 09 31 pm" src="https://cloud.githubusercontent.com/assets/12079825/19640903/7323ba3a-99fc-11e6-8359-6a45753dbb28.png">
- No applications found and No currently pending logs:

<img width="1280" alt="screen shot 2016-10-24 at 3 24 26 pm" src="https://cloud.githubusercontent.com/assets/12079825/19641364/03a2cb04-99fe-11e6-87d6-d09587fc6201.png">

Author: Vinayak <vijoshi5@in.ibm.com>

Closes #15410 from vijoshi/SAAS-608_master.

1 files changed, 24 insertions, 0 deletions

diff --git a/core/src/main/resources/org/apache/spark/ui/static/historypage-common.js b/core/src/main/resources/org/apache/spark/ui/static/historypage-common.js
new file mode 100644
index 0000000000..55d540d831
--- /dev/null
+++ b/core/src/main/resources/org/apache/spark/ui/static/historypage-common.js
@@ -0,0 +1,24 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+$(document).ready(function() {
+    if ($('#last-updated').length) {
+      var lastUpdatedMillis = Number($('#last-updated').text());
+      var updatedDate = new Date(lastUpdatedMillis);
+      $('#last-updated').text(updatedDate.toLocaleDateString()+", "+updatedDate.toLocaleTimeString())
+    }
+});