Systemui: Recents - do not add search widget on recents if widget is lost.

We have reports that sometimes under special circumstances the widget gets lost
and the view is added nevertheless

Ensure that if the widget loading fails that the id is set back to -1 to remove
the view.

Change-Id: I62f8dcea19817a243a001c80b6a4ab7b1e31a990
Frameworks: Actually start to use HEADS_UP_REQUESTED extra

Prepairing slim heads up feature, we do this here to allow apps to
send a heads up notification no matter what.

Google introduced this flag but is not using it in the actual API

Take HEADS_UP_REQUESTED into account to indicate that this notification
is a good heads up candidate.

How to use it you can see in email or mms app

Change-Id: I4a29404122ae12ab9b95e1d223911078a360b44e