Fix regression in unfreezing the recent task list

- On certain devices, the HWC ScreenDecorOverlay is full size (not just
  the corners), and the previous logic to determine if a touch is
  in an app inadvertently finds this window (it's above everything
  else) and as a result incorrectly assumes that the touch is not going
  to an app window.  Instead, use the alternate existing method for
  finding the app window under a point which takes into account the
  touchable region of the window.

Fixes: 268285353
Test: Quickswitch to previous app, tap on the app and ensure task
      list is unfrozen (you can't quickswitch back to previous app)
Change-Id: I2580dc8e8ed463c6d994f44382138ce2ba5bf890
Merged-In: I2580dc8e8ed463c6d994f44382138ce2ba5bf890