Fix bubble shows empty contents after rotating the device.

When a virtual display turns on or off, DisplayManagerService notifies
it to WindowManagerService via messaging. Since the messaging is handled
asynchronously, the virtual display status might be changed again
before WindowManagerService gets notified, so WindowManagerService
might miss that the virtual display stauts is changed.

In order to trigger ITaskStackListner#onSingleTaskDisplayDrawn even when
WindowManagerService misses virtual display status change, we prepare
an app transition TRANSIT_SHOW_SINGLE_TASK_DISPLAY when moving a task
to front.

Bug: 158675422
Test: manual. Expand bubble, rotate device and check app transitions.
Change-Id: Ib48d4faab8fa0cef88074593b0ae1a3b7615d9c0