YARN-1007. Enhance History Reader interface for Containers. Contributed by Mayank Bansal.
svn merge --ignore-ancestry -c 1510001 ../../branches/YARN-321-old/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/YARN-321@1556723 13f79535-47bb-0310-9956-ffa450edef68