Revert r151669 and r155589 as non-Aura Metro mode is gone
Now TSF-related code is completely consolidated into the metro_driver process. We can safely revert the following CLs:
- r155589 : Call TSF-based UI message pump APIs by introducing an injection mechanism into MessageLoopForUI.
- r151669 : Introduce base::win::IsTSFAwareRequired() which indicates if TSF-awareness is required or not.
TEST=manually done on Windows 8.1