Improve SendToRietveld to hardcode less function arguments.

TEST=manually tested that gcl works on both chromium and non-chromium rietveld instances
BUG=none

Review URL: http://codereview.chromium.org/5015005

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@66499 0039d316-1c4b-4281-b951-d872f2087c98