It has happened (possibly due to a bug in deps2submodules.py) that
people have wound up with an empty submodule.<name>.url entry in
their git config.  If that happens, crup-runner.sh should update it.

TBR=adamk@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/116583003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@240973 0039d316-1c4b-4281-b951-d872f2087c98