Icon support comes to Notification.

  And you may ask yourself: what is that beautiful icon?
  And you may ask yourself: where does that API go to?
  And you may ask yourself: is it a resource? is it a Bitmap?
  And you may say to yourself: my god, what have I done

(This patch fixes a number of bugs in the initial
implementation, but other than that, it's the same as it
ever was.)

Bug: 18568715
Bug: 21141842
Change-Id: I1d3f9427abd7f0bb57e533fcfac708851ff644b6