Make enterTabSwitcher in TabUiTestHelper less flaky

Bug: 1019727
Change-Id: I4a07764eb71c4ff7f843602795e35d7262120c4d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1890393Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Commit-Queue: Yue Zhang <yuezhanggg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#711436}

chrome/android/features/tab_ui/javatests/src/org/chromium/chrome/browser/tasks/tab_management/TabUiTestHelper.java

@@ -59,7 +59,10 @@ public class TabUiTestHelper {
     static void enterTabSwitcher(ChromeTabbedActivity cta) {
         OverviewModeBehaviorWatcher showWatcher = createOverviewShowWatcher(cta);
         assertFalse(cta.getLayoutManager().overviewVisible());
-        onView(withId(R.id.tab_switcher_button)).perform(click());
+        // TODO(crbug.com/1019727) Figure out a better way to wait until isCompletelyDisplayed() is
+        // true in espresso.
+        TestThreadUtils.runOnUiThreadBlocking(
+                () -> { cta.findViewById(R.id.tab_switcher_button).performClick(); });
         showWatcher.waitForBehavior();
     }
 
@@ -171,4 +174,4 @@ public class TabUiTestHelper {
             }
         }
     }
-}
+}
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