base

Reset mPointerIconShape properly on window manager.

Sometimes mPointerIconShape wrongly remember old icon shape,
so that it fails to specify the icon on some situation, such
as reported in the bug.
- task == null: happening tasks are overlapping and mouse moves
  directly from an edge of a task to inside of another task
- hover_exit: happening the mouse moves outside of any tasks.
  I believe I added this line but anyways it's been lost at
  some point.

Bug: 26011155
Change-Id: I0bdc345a28089bd13443d9b7b8e7c770e56247f3