These are run for a given dependency after it has been synced but before its
DEPS have been synced. This will help to switch Chromium to depend on Skia's
git repository (skia:1638).

Review URL: https://codereview.chromium.org/25322002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@228651 0039d316-1c4b-4281-b951-d872f2087c98