Notify top task of each display.

When there are mutltiple top tasks (e.g. one semi-transparent or
partially visible activity over a fullscreen one), UXR attempts to
launch blocking activity. This isn't ideal when the one on top (z-axis)
is DO.

Bug: 119996644
Test: verified on device
Change-Id: I6c08c2c8acb71148457505a545812a1d2bcb0d96
2 files changed