Otherwise it breaks naked --revision usage. One example issue is linux_chromeos
applying the revision to cros_deps instead of src.

TBR=dpranke@chromium.org
BUG=100335
TEST=


Review URL: http://codereview.chromium.org/8298002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@105522 0039d316-1c4b-4281-b951-d872f2087c98