Before, the size compat UI is reparent to Task with its original layer
(likely 1), which may not be the higheset layer when the Task contains
more than one children.
Fix: 181541449
Bug: 178327644
Test: verify with launching a non-resizable activity from another
Change-Id: I9e812ca8c0c1fd5b93a6e074a5e4df164c8fa03b