Fixed how FillEventHistory is reset and clarified javadoc.

Test: existing CtsAutoFillServiceTestCases pass
Test: checkFillSelectionIsResetAfterReturningNull()
Test: checkFillSelectionIsResetAfterReturningError()
Test: checkFillSelectionIsResetAfterTimeout()

Bug: 62802026

Change-Id: I389d95fc13c08f1056960e5f67e131c8dc306401
5 files changed