Fix flaky DeferredStartupHandler test waiting

We can get into a situation where an Activity is finished before
Deferred startup finishes, then the old DeferredStartupHandler finishes
during startup of the next test and a new instance is created before
we wait for deferred startup completion. The solution is just to hold
onto the DeferredStartupHandler instance in tests during startup to
ensure a new instance isn't created.

The test that's actually flaky under these circumstances is
TabbedActivityLaunchCauseMetricsTest#testMainIntentMetrics

Change-Id: I4e172f77c3ebad45f5b3236b68614b2b152c718c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2643030Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#846279}

chrome/android/features/start_surface/internal/javatests/src/org/chromium/chrome/features/start_surface/StartSurfaceLayoutTest.java

@@ -91,9 +91,7 @@ import org.chromium.base.test.util.Feature;
 import org.chromium.base.test.util.FlakyTest;
 import org.chromium.base.test.util.MinAndroidSdkLevel;
 import org.chromium.base.test.util.Restriction;
-import org.chromium.base.test.util.ScalableTimeout;
 import org.chromium.chrome.browser.ChromeTabbedActivity;
-import org.chromium.chrome.browser.DeferredStartupHandler;
 import org.chromium.chrome.browser.compositor.layouts.Layout;
 import org.chromium.chrome.browser.compositor.layouts.StaticLayout;
 import org.chromium.chrome.browser.compositor.layouts.content.TabContentManager;
@@ -1933,9 +1931,8 @@ public class StartSurfaceLayoutTest {
         AtomicBoolean tabModelRestoreCompleted = new AtomicBoolean(false);
         AtomicBoolean normalModelIsEmpty = new AtomicBoolean(true);
 
-        DeferredStartupHandler.setExpectingActivityStartupForTesting();
-        ChromeTabbedActivity newActivity =
-                ApplicationTestUtils.recreateActivity(mActivityTestRule.getActivity());
+        mActivityTestRule.recreateActivity();
+        ChromeTabbedActivity newActivity = mActivityTestRule.getActivity();
 
         new TabModelSelectorTabModelObserver(newActivity.getTabModelSelector()) {
             @Override
@@ -1969,9 +1966,7 @@ public class StartSurfaceLayoutTest {
                 "New Activity current TabModel is not incognito");
         TestThreadUtils.runOnUiThreadBlocking(IncognitoUtils::closeAllIncognitoTabs);
 
-        assertTrue("Deferred startup never completed",
-                DeferredStartupHandler.waitForDeferredStartupCompleteForTesting(
-                        ScalableTimeout.scaleTimeout(CriteriaHelper.DEFAULT_MAX_TIME_TO_POLL)));
+        assertTrue("Deferred startup never completed", mActivityTestRule.waitForDeferredStartup());
 
         CriteriaHelper.pollUiThread(()
                                             -> tabModelRestoreCompleted.get(),

chrome/android/features/start_surface/internal/javatests/src/org/chromium/chrome/features/start_surface/StartSurfaceTest.java

@@ -90,9 +90,7 @@ import org.chromium.base.test.util.DisableIf;
 import org.chromium.base.test.util.DisabledTest;
 import org.chromium.base.test.util.Feature;
 import org.chromium.base.test.util.Restriction;
-import org.chromium.base.test.util.ScalableTimeout;
 import org.chromium.chrome.browser.ChromeTabbedActivity;
-import org.chromium.chrome.browser.DeferredStartupHandler;
 import org.chromium.chrome.browser.compositor.layouts.phone.StackLayout;
 import org.chromium.chrome.browser.feed.FeedSurfaceCoordinator;
 import org.chromium.chrome.browser.feed.FeedSurfaceMediator;
@@ -177,7 +175,6 @@ public class StartSurfaceTest {
      * because of its {@link org.chromium.chrome.browser.tab.Tab} dependency.
      */
     private void startMainActivityFromLauncher() {
-        DeferredStartupHandler.setExpectingActivityStartupForTesting();
         Intent intent = new Intent(Intent.ACTION_MAIN);
         intent.addCategory(Intent.CATEGORY_LAUNCHER);
         mActivityTestRule.prepareUrlIntent(intent, null);
@@ -1221,9 +1218,7 @@ public class StartSurfaceTest {
                         && mActivityTestRule.getActivity().getLayoutManager().overviewVisible());
         mActivityTestRule.waitForActivityNativeInitializationComplete();
 
-        assertTrue("Deferred startup never completed",
-                DeferredStartupHandler.waitForDeferredStartupCompleteForTesting(
-                        ScalableTimeout.scaleTimeout(20000L)));
+        assertTrue("Deferred startup never completed", mActivityTestRule.waitForDeferredStartup());
 
         boolean isInstantStart = TabUiFeatureUtilities.supportInstantStart(false);
         Assert.assertEquals(1,

chrome/android/java/src/org/chromium/chrome/browser/DeferredStartupHandler.java

@@ -79,15 +79,18 @@ public class DeferredStartupHandler {
      * Avoid using CriteriaHelper for waiting for deferred tasks to complete, as the act of polling
      * can prevent the Looper from going idle, preventing the tasks from running.
      *
-     * You must call {@link #setExpectingActivityStartupForTesting()} before calling this.
+     * You should wait until the activity has posted its deferred startup tasks before calling this
+     * function to avoid races.
      *
      * @return Whether deferred startup has been completed before the timeout expires.
      */
     public static boolean waitForDeferredStartupCompleteForTesting(long timeoutMillis) {
         ThreadUtils.assertOnBackgroundThread();
         // sInstance could become null while executing this function, so keep a ref here.
-        DeferredStartupHandler instance =
-                ThreadUtils.runOnUiThreadBlockingNoException(() -> { return sInstance; });
+        DeferredStartupHandler instance = ThreadUtils.runOnUiThreadBlockingNoException(() -> {
+            if (sInstance != null) sInstance.mLatchForTesting = new CountDownLatch(1);
+            return sInstance;
+        });
         // Tasks completed and instance was cleared before we started waiting.
         if (instance == null) return true;
         assert instance.mLatchForTesting != null;
@@ -97,9 +100,4 @@ public class DeferredStartupHandler {
             return false;
         }
     }
-
-    public static void setExpectingActivityStartupForTesting() {
-        ThreadUtils.runOnUiThreadBlocking(
-                () -> { getInstance().mLatchForTesting = new CountDownLatch(1); });
-    }
 }

chrome/android/java/src/org/chromium/chrome/browser/app/ChromeActivity.java

@@ -2468,4 +2468,9 @@ public abstract class ChromeActivity<C extends ChromeActivityComponent>
     public Configuration getSavedConfigurationForTesting() {
         return mConfig;
     }
+
+    @VisibleForTesting
+    public boolean deferredStartupPostedForTesting() {
+        return mDeferredStartupPosted;
+    }
 }

chrome/android/javatests/src/org/chromium/chrome/browser/firstrun/FirstRunIntegrationTest.java

@@ -336,7 +336,6 @@ public class FirstRunIntegrationTest {
         // policy set in this test case.
         FirstRunStatus.setFirstRunSkippedByPolicy(true);
 
-        DeferredStartupHandler.setExpectingActivityStartupForTesting();
         Intent intent = CustomTabsTestUtils.createMinimalCustomTabIntent(mContext, "about:blank");
         mContext.startActivity(intent);
         CustomTabActivity activity = waitForActivity(CustomTabActivity.class);
@@ -344,6 +343,7 @@ public class FirstRunIntegrationTest {
 
         // DeferredStartupHandler could not finish with CriteriaHelper#DEFAULT_MAX_TIME_TO_POLL.
         // Use longer timeout here to avoid flakiness. See https://crbug.com/1157611.
+        CriteriaHelper.pollUiThread(() -> activity.deferredStartupPostedForTesting());
         Assert.assertTrue("Deferred startup never completed",
                 DeferredStartupHandler.waitForDeferredStartupCompleteForTesting(
                         ScalableTimeout.scaleTimeout(DEFERRED_START_UP_POLL_TIME)));

chrome/test/android/javatests/src/org/chromium/chrome/test/ChromeActivityTestRule.java

@@ -199,7 +199,6 @@ public class ChromeActivityTestRule<T extends ChromeActivity> extends BaseActivi
      * Similar to #launchActivity(Intent), but waits for the Activity tab to be initialized.
      */
     public void startActivityCompletely(Intent intent) {
-        DeferredStartupHandler.setExpectingActivityStartupForTesting();
         launchActivity(intent);
         waitForActivityNativeInitializationComplete();
 
@@ -214,15 +213,18 @@ public class ChromeActivityTestRule<T extends ChromeActivity> extends BaseActivi
             NewTabPageTestUtils.waitForNtpLoaded(tab);
         }
 
-        Assert.assertTrue("Deferred startup never completed. Did you try to start an Activity "
-                        + "that was already started?",
-                DeferredStartupHandler.waitForDeferredStartupCompleteForTesting(
-                        ScalableTimeout.scaleTimeout(CriteriaHelper.DEFAULT_MAX_TIME_TO_POLL)));
+        Assert.assertTrue(waitForDeferredStartup());
 
         Assert.assertNotNull(tab);
         Assert.assertNotNull(tab.getView());
     }
 
+    public boolean waitForDeferredStartup() {
+        CriteriaHelper.pollUiThread(() -> getActivity().deferredStartupPostedForTesting());
+        return DeferredStartupHandler.waitForDeferredStartupCompleteForTesting(
+                ScalableTimeout.scaleTimeout(CriteriaHelper.DEFAULT_MAX_TIME_TO_POLL));
+    }
+
     @Override
     public void launchActivity(Intent startIntent) {
         // Avoid relying on explicit intents, bypassing LaunchIntentDispatcher, created by null