Didn't have any shell=True for git.bat/cmd.

Was able to upload https://codereview.chromium.org/1151373003 after
this CL (though the printed description didn't make it to Rietveld,
not sure if it normally does that.)

R=maruel@chromium.org

Review URL: https://codereview.chromium.org/1151373003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@295397 0039d316-1c4b-4281-b951-d872f2087c98