This flakiness is due to race of config updates when WindowContext attaches to
DisplyArea.
This CL fixed it by:
1. Don't dispatch config updates to the client side when registering to
DA. We have reported the value by the return value of
#attachWindowContextToDisplayArea.
2. Use Handler#runWithScissors when attahing DA or DC. It can prevent
WindowContext reports stale config values and also guarantee the order of
onConfigurationChanged call.
Bug: 190019118
fixes: 228911504
Test: atest RegisterComponentCallbacksTest --iterations
Test: atest WindowContextTest WindowContextTests
Test: atest WindowMetricsWindowContextTests
Change-Id: I496d00bbfdc20b9bbf433d5d8ec65bf1f46d3dd3
edf1b37a08