Fixes redirects to external apps when navigating from PWA.

chrome/android/javatests/src/org/chromium/chrome/browser/webapps/TopActivityListener.java

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser.webapps;
 
 import android.app.Activity;
 
 import org.junit.rules.TestRule;
 import org.junit.runner.Description;
 import org.junit.runners.model.Statement;
 
 import org.chromium.base.ActivityState;
 import org.chromium.base.ApplicationStatus;
 import org.chromium.base.ApplicationStatus.ActivityStateListener;
 import org.chromium.content.browser.test.util.Criteria;
 import org.chromium.content.browser.test.util.CriteriaHelper;
 
+import java.util.concurrent.TimeUnit;
+
 import javax.annotation.Nullable;
 
 /**
  * Test rule tracking which Chrome activity is currently at the top of the task.
  */
 public class TopActivityListener implements TestRule {
+    private static final long ONE_SECOND_IN_MILLIS = TimeUnit.SECONDS.toMillis(1);
+
     private final ActivityStateListener mListener = new ActivityStateListener() {
         @Override
         public void onActivityStateChange(Activity activity, int newState) {
             if (newState == ActivityState.RESUMED) {
                 mMostRecentActivity = activity;
+            } else if (activity == mMostRecentActivity && newState == ActivityState.PAUSED) {
+                mMostRecentActivity = null;
+                mTimeWhenSetToNullMillis = System.currentTimeMillis();
             }
         }
     };
 
+    private long mTimeWhenSetToNullMillis;
     private Activity mMostRecentActivity;
 
     @Override
     public Statement apply(final Statement base, Description description) {
         return new Statement() {
             @Override
             public void evaluate() throws Throwable {
                 ApplicationStatus.registerStateListenerForAllActivities(mListener);
                 base.evaluate();
                 ApplicationStatus.unregisterActivityStateListener(mListener);
             }
         };
     }
 
     @Nullable
     public Activity getMostRecentActivity() {
         return mMostRecentActivity;
     }
 
     @SuppressWarnings("unchecked")
     public <T extends Activity> T waitFor(final Class<T> expectedActivityClass) {
         CriteriaHelper.pollUiThread(new Criteria() {
             @Override
             public boolean isSatisfied() {
                 return mMostRecentActivity != null

[Ted C, 2017/07/10 18:10:15]

why not just use ApplicationStatus.getLastTrackedFocusedActivity() ?

[piotrs, 2017/07/10 23:40:54]

An Oversight. I deleted this whole class.

                         && expectedActivityClass.isAssignableFrom(mMostRecentActivity.getClass());
             }
         });
         return (T) mMostRecentActivity;
     }
+
+    public void waitForExternalApp() {
+        CriteriaHelper.pollUiThread(new Criteria() {
+            @Override
+            public boolean isSatisfied() {
+                return mMostRecentActivity == null

[Ted C, 2017/07/10 18:10:15]

Just use ApplicationStatus.getStateForApplication == HAS_STOPPED_ACTIVITIES ||
HAS_DESTROYED_ACTIVITIES

[piotrs, 2017/07/10 23:40:54]

An Oversight. I deleted this whole class.

+                        && (System.currentTimeMillis() - mTimeWhenSetToNullMillis)

[Ted C, 2017/07/10 18:10:15]

this delay is very much specific to your test.  Instead, don't assertEquals in
your test about your expectation but use CriteriaHelper to check there for you.

[piotrs, 2017/07/10 23:40:54]

I don't quite follow. My intention was to ensure that we are really outside of
Chrome instead of catching a glimpse of being in between activities (previous
got stopped while the new one isn't started yet). Therefore the time check,
which I don't see as specific to my test.

But I'm probably a little paranoid. Removed that now.

[Ted C, 2017/07/11 00:05:38]

In general, any explicit time is likely to give you grief in Android land.  What
runs in 10s of milliseconds on a high end device could take 100s on the lowest
end.  Whenever I see these sorts of things, I push hard towards CriteriaHelper
(which has scaled timeouts based on bot configuration) and is a bit more
flexible.  Removing is good though :-P.

You are right that there could be a glimpse between activities, but that should
be purely with what is rendered to the screen and not what Chrome's awareness of
it's state is.

Just clarifying "hopefully".

+                        > ONE_SECOND_IN_MILLIS;
+            }
+        });
+    }
 }