This makes the commit logs much more useful for a build sheriff. Not only he
sees who committed the CL but see who approved it directly at the log. This
should help build sheriffs when they fail to contact the author and want to
fallback on the reviewer for quick questions.

R=dpranke@chromium.org
BUG=76730

Review URL: https://chromiumcodereview.appspot.com/13800021

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@196786 0039d316-1c4b-4281-b951-d872f2087c98