If the parent of the commit is no longer the tip of the target branch,
it becomes possible to rebase the change on that branch. With this
change, the change metadata section shows an out of date indicator next
to the abbreviated parent hash.
The indicator is only shown on non-merge changes for authenticated
users.
Bug: Issue 4655
Change-Id: I6cb4d280352bb37214b853760c6723597690010a