This is for situations where the solution is checked out by another SCM
mechanism (e.g. update-webkit or just svn co) but we want to use gclient to
fetch the dependencies.

Review URL: http://codereview.chromium.org/211057

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@26876 0039d316-1c4b-4281-b951-d872f2087c98