make sure that Activity is ready before count down

Bug: 6339033
Change-Id: Idd98955b80a8502e6312bfbf517381e8294f8c5c
diff --git a/tests/tests/accessibilityservice/src/android/accessibilityservice/cts/AccessibilityActivityTestCase.java b/tests/tests/accessibilityservice/src/android/accessibilityservice/cts/AccessibilityActivityTestCase.java
index e6ef33d..97f4359 100644
--- a/tests/tests/accessibilityservice/src/android/accessibilityservice/cts/AccessibilityActivityTestCase.java
+++ b/tests/tests/accessibilityservice/src/android/accessibilityservice/cts/AccessibilityActivityTestCase.java
@@ -105,6 +105,7 @@
             @Override
             public void run() {
                 getActivity();
+                getInstrumentation().waitForIdleSync();
             }
         },
                 new AccessibilityEventFilter() {