Launch Activity by using ActivityScenario instead of ActivityTestRule Also, wait for the device to be idle after launching an activity Bug: 335201560 Test: atest AccessibilityDisplayProxyTest --iterations 50 Test: atest AccessibilityEmbeddedHierarchyTest --iterations 50 Flag: TEST_ONLY Change-Id: I3a75efd38d580be71a5aaf6f2c78013e5ff8b8e5