This CL fixes some issues with map-branches:
* Branches with no upstream were not being shown.
* -vv from a detached HEAD would crash
* GONE upstreams would crash when git cleaned up in a way that caused
  hash_one to fail

This CL also adds a blue coloring to branches that start with
'branch-heads' for Chromium release branches.

BUG=416530

Review URL: https://codereview.chromium.org/576423002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@292083 0039d316-1c4b-4281-b951-d872f2087c98