Sort failure stream by latest "firstFailingRevisions" first.

We first look at the revision of the active tree, and then at all other
revisions.

failures without a revision go to the end.

BUG=399718
R=ojan@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/451633005

git-svn-id: svn://svn.chromium.org/blink/trunk@179743 bbb929c8-8fbe-4397-9dbb-9b2b20218538