[SPARK-5768] [WEB UI] Fix for incorrect memory in Spark UI

Fix for incorrect memory in Spark UI as per SPARK-5768

Author: Joshi <rekhajoshm@gmail.com>
Author: Rekha Joshi <rekhajoshm@gmail.com>

Closes #6972 from rekhajoshm/SPARK-5768 and squashes the following commits:

b678a91 [Joshi] Fix for incorrect memory in Spark UI
2fe53d9 [Joshi] Fix for incorrect memory in Spark UI
eb823b8 [Joshi] SPARK-5768: Fix for incorrect memory in Spark UI
0be142d [Rekha Joshi] Merge pull request #3 from apache/master
106fd8e [Rekha Joshi] Merge pull request #2 from apache/master
e3677c9 [Rekha Joshi] Merge pull request #1 from apache/master

(cherry picked from commit 085a721)
Signed-off-by: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Author: rekhajoshm

core/src/main/scala/org/apache/spark/ui/ToolTips.scala

@@ -35,6 +35,10 @@ private[spark] object ToolTips {
 
   val OUTPUT = "Bytes and records written to Hadoop."
 
+  val STORAGE_MEMORY =
+    "Memory used / total available memory for storage of data " +
+      "like RDD partitions cached in memory. "
+
   val SHUFFLE_WRITE =
     "Bytes and records written to disk in order to be read by a shuffle in a future stage."
 

core/src/main/scala/org/apache/spark/ui/exec/ExecutorsPage.scala

@@ -67,7 +67,7 @@ private[ui] class ExecutorsPage(
           <th>Executor ID</th>
           <th>Address</th>
           <th>RDD Blocks</th>
-          <th>Memory Used</th>
+          <th><span data-toggle="tooltip" title={ToolTips.STORAGE_MEMORY}>Storage Memory</span></th>
           <th>Disk Used</th>
           <th>Active Tasks</th>
           <th>Failed Tasks</th>