ViewRootImpl: Use mWindowAttributes directly for BBQ

The logic we are using to handle the params == null case doesn't make
sense, params=null just indicates nothing was changing on this relayout
and so we avoid passing to WM, not that we should default the format. We
can just use mWindowAttributes directly to avoid this problem.

Test: Existing tests pass
Bug: 190483641
Change-Id: I4a765914eb8ca33a432fc808af96847bb78fb054