YARN-934. Updated patch for HistoryWriter to split the write operations into a startOp and a finishOp. Contributed by Zhijie Shen.
YARN-947. Updated patch to have separate data object for startOp and finishOp. Contributed by Zhijie Shen.
YARN-956. Updated patch for In-memory Storage after the above two changes.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/YARN-321@1536940 13f79535-47bb-0310-9956-ffa450edef68
YARN-975. Added a file-system implementation for HistoryStorage. Contributed by Zhijie Shen.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/YARN-321@1536942 13f79535-47bb-0310-9956-ffa450edef68