Finish when browsed root goes away.

If we're browsing a specific root, and that root went away, typically
due to formatting.

Skipped auto-merging this CL to master last night as it was causing
a merge conflict.  Cherry-picking it to master today (with the conflict
resolved).

Bug: 21831184
Change-Id: Ie07607a81e32a7d82c88ad382658a471d47b905d