Bug 961495 - [Task Manager] Clean up opening transition r=alive,aus
Revert "Bug 913782 - [Keyboard] Build time default keyboard selection work for"

This reverts commit 41891f2f87d6304410776e043d53b36a13f26cad.
Merge pull request #15657 from KevinGrandon/bug_961495_to_master

Bug 961495 - [Task Manager] Opening transition