This tool can automatically set up the necessary git-svn metadata for our
repos that live in SVN but are mirrored to Chrome.

R=iannucci@chromium.org, tandrii@chromium.org
BUG=418973

Review URL: https://codereview.chromium.org/611253003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@292241 0039d316-1c4b-4281-b951-d872f2087c98