It runs it by specifying BASE/HEAD to stay at the current revision.
This works around the lack of gclient sync when a DEPS file is applied on the
Try Server when triggered from Rietveld. This was handled my the Try Server
inside scripts/slave/chromium_command.py manually in the case a 'patch' is
specified.

TBR=rogerta@chromium.org
BUG=


Review URL: https://chromiumcodereview.appspot.com/10918264

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@157110 0039d316-1c4b-4281-b951-d872f2087c98