Include all hung bots alerts in Trooper tree.

Currently, chromium hung bots and blink hung bots are shown in their
corresponding views. With this change, all hung bots will show up in the Trooper
view. This includes the chromium and blink ones, but also others other trees
(e.g. non-closers).

BUG=412189

Review URL: https://codereview.chromium.org/661463004

git-svn-id: svn://svn.chromium.org/blink/trunk@183850 bbb929c8-8fbe-4397-9dbb-9b2b20218538