Throttle content changed events per source

Previous attempt Ic18cd4aa310ab37e40c6623625b59b4b9ebfea2f caused a
perormance regression.
To mitigate, this allows event throttling when the source node is the
same as the previous event.

Bug: 277305460
Bug: 280057969
Test: CtsAccessibilityTestCases CtsAccessibilityServiceTestCases
Test: android.inputmethod.ImePerfTest#testShowImeCold
Change-Id: Ieb506ca2ee8aee7a529183507e04382d167304b3
1 file changed