Add hung bots to sheriff-o-matic view

Add another category of failure cards that display bots that have
been running or offline over a threshold of time. This is special-
cased for chromium.webkit & blink to start.

Also removing ct-revision-details since it's effectively obsoleted
by this change.

BUG=399957
NOTRY=true

Review URL: https://codereview.chromium.org/555263004

git-svn-id: svn://svn.chromium.org/blink/trunk@181700 bbb929c8-8fbe-4397-9dbb-9b2b20218538