Add tree status to garden-o-matic.

As gardener, I kept not noticing that the tree got auto-closed.
Update this every 30 seconds instead of every 10 minutes like the
other updates.

Review URL: https://codereview.chromium.org/27029008

git-svn-id: svn://svn.chromium.org/blink/trunk@159627 bbb929c8-8fbe-4397-9dbb-9b2b20218538