This method is necessary to allow good code organization (i.e., unittests live
adjacent to the source files they test) in the new infra.git repository.

R=maruel@chromium.org

Review URL: https://codereview.chromium.org/281013002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@270564 0039d316-1c4b-4281-b951-d872f2087c98