Create content::WebContentsDestroyedWatcher, use it in many tests.

chrome/browser/notifications/notification_browsertest.cc

 // Copyright (c) 2012 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.
 
 #include <deque>
 #include <string>
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/command_line.h"
@@ skipping 838 matching lines @@
 
   // Test that user can close tab when infobar present.
   ui_test_utils::NavigateToURLWithDisposition(
       browser(),
       GURL("about:blank"),
       NEW_BACKGROUND_TAB,
       ui_test_utils::BROWSER_TEST_WAIT_FOR_TAB);
   browser()->tab_strip_model()->ActivateTabAt(0, true);
   ui_test_utils::NavigateToURL(browser(), GetTestPageURL());
   ASSERT_TRUE(RequestPermissionAndWait(browser()));
-  content::WindowedNotificationObserver observer(
-      content::NOTIFICATION_WEB_CONTENTS_DESTROYED,
-      content::NotificationService::AllSources());
+  content::WebContentsDestroyedWatcher destroyed_watcher(
+      browser()->tab_strip_model()->GetWebContentsAt(0));
   browser()->tab_strip_model()->CloseWebContentsAt(0,
                                                    TabStripModel::CLOSE_NONE);
-  observer.Wait();
+  destroyed_watcher.Wait();
 }
 
 IN_PROC_BROWSER_TEST_F(
     NotificationsTest,
     TestNavigateAwayWithPermissionInfobar) {
   ASSERT_TRUE(embedded_test_server()->InitializeAndWaitUntilReady());
 
   // Test navigating away when an infobar is present,
   // then trying to create a notification from the same page.
   ui_test_utils::NavigateToURLWithDisposition(
@@ skipping 67 matching lines @@
     const std::deque<Balloon*>& balloons = GetActiveBalloons();
     ASSERT_EQ(1U, balloons.size());
     Balloon* balloon = balloons[0];
     const Notification& notification = balloon->notification();
     GURL EXPECTED_ICON_URL = embedded_test_server()->GetURL(kExpectedIconUrl);
     EXPECT_EQ(EXPECTED_ICON_URL, notification.icon_url());
     EXPECT_EQ(ASCIIToUTF16("Title2"), notification.title());
     EXPECT_EQ(ASCIIToUTF16("Body2"), notification.message());
   }
 }