We've synced our fork of repo to upstream. This change copies the new
version into depot_tools.

BUG=chromium:339665
TEST=repo sync works

Review URL: https://codereview.chromium.org/146723003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@249277 0039d316-1c4b-4281-b951-d872f2087c98