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 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);
@@ skipping 10 matching lines @@
     public <T extends Activity> T waitFor(final Class<T> expectedActivityClass) {
         CriteriaHelper.pollUiThread(new Criteria() {
             @Override
             public boolean isSatisfied() {
                 return mMostRecentActivity != null
                         && expectedActivityClass.isAssignableFrom(mMostRecentActivity.getClass());
             }
         });
         return (T) mMostRecentActivity;
     }
+
+    public void waitForExternalApp() {
+        CriteriaHelper.pollUiThread(new Criteria() {
+            @Override
+            public boolean isSatisfied() {
+                return mMostRecentActivity == null
+                        && (System.currentTimeMillis() - mTimeWhenSetToNullMillis)
+                        > TimeUnit.SECONDS.toMillis(1);

[dominickn, 2017/07/07 05:56:04]

Nit: possibly put the 1 as a static class level constant for clarity.

[piotrs, 2017/07/09 23:43:38]

Done.

+            }
+        });
+    }
 }