Cleaning up UI jank while quick switching

Moving a few calls into the UI helper executor thread, as per the associated bug. duplicated the lines so the synchronous nature of clearing previous state wouldn't affect potential timings.

Test: local testing, rotating screen. quick switching apps.

Bug: 257470365
Change-Id: I59abad9ba51c0b19d467646752aa34ae7ef3ec1d
1 file changed