V8 Buildbot: Make test262-es6 a tree closer.
V8 Buildbot: Make test262-es6 a tree closer.

TBR=stip@chromium.org

Review URL: https://codereview.chromium.org/743933002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@293021 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build