Support entering PiP from live tile

When finish the recents animation, send user leave hint if live tile is
currently on. Note that we force the PiP window fades in in this case.

Video: http://recall/-/aaaaaabFQoRHlzixHdtY/bLoRpbgcyZBt1UiQPZEXcF
Bug: 187421300
Test: manual, see video
Change-Id: I07bc307c5eb895cd23b764af92e39ff7e6f8e805