DO NO MERGE -- Revert the following two commits as they're causing flickering
When double tapping Recents, need to reinvestigate.
b/30831873
b/30790402
Revert "Clear WS.mDestroying on AWT.clearAnimatingFlags"
This reverts commit c2661e52.
Revert "Some fixes for transition animation selection"
This reverts commit 73e9bc3f.