The depot_tools and nacl recipes aren't setting up git-svn
properly. There is no git-svn branch in the git mirror for
depot-tools and nacl, just master.
As a consequence "fetch depot-tools" ends up recreating all
the objects from svn taking much more time than it should.

BUG=

Review URL: https://codereview.chromium.org/183743010

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@254506 0039d316-1c4b-4281-b951-d872f2087c98