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

chrome/browser/unload_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.
 
 #if defined(OS_POSIX)
 #include <signal.h>
 #endif
 
 #include "base/command_line.h"
 #include "base/logging.h"
@@ skipping 388 matching lines @@
   content::WindowedNotificationObserver load_stop_observer(
       content::NOTIFICATION_LOAD_STOP,
       content::NotificationService::AllSources());
   content::SimulateMouseClick(
       browser()->tab_strip_model()->GetActiveWebContents(), 0,
       WebKit::WebMouseEvent::ButtonLeft);
   observer.Wait();
   load_stop_observer.Wait();
   CheckTitle("popup");
 
-  content::WindowedNotificationObserver tab_close_observer(
-      content::NOTIFICATION_WEB_CONTENTS_DESTROYED,
-      content::NotificationService::AllSources());
+  content::WebContentsDestroyedWatcher destroyed_watcher(
+      browser()->tab_strip_model()->GetActiveWebContents());
   chrome::CloseTab(browser());
-  tab_close_observer.Wait();
+  destroyed_watcher.Wait();
 
   CheckTitle("only_one_unload");
 }
 
 class FastUnloadTest : public UnloadTest {
  public:
   virtual void SetUpCommandLine(CommandLine* command_line) OVERRIDE {
     UnloadTest::SetUpCommandLine(command_line);
     command_line->AppendSwitch(switches::kEnableFastUnload);
   }
@@ skipping 63 matching lines @@
     DISABLED_UnloadHidden
 #else
 #define MAYBE_UnloadHidden \
     UnloadHidden
 #endif
 IN_PROC_BROWSER_TEST_F(FastUnloadTest, MAYBE_UnloadHidden) {
   NavigateToPage("no_listeners");
   NavigateToPageInNewTab("unload_sets_cookie");
   EXPECT_EQ("", GetCookies("no_listeners"));
 
+  content::WebContentsDestroyedWatcher destroyed_watcher(
+      browser()->tab_strip_model()->GetActiveWebContents());
+
   {
     base::RunLoop run_loop;
     FastTabCloseTabStripModelObserver observer(
         browser()->tab_strip_model(), &run_loop);
     chrome::CloseTab(browser());
     run_loop.Run();
   }
 
   // Check that the browser only has the original tab.
   CheckTitle("no_listeners");
   EXPECT_EQ(1, browser()->tab_strip_model()->count());
 
-  // Show that the web contents to go away after the was removed.
-  // Without unload-detached, this times-out because it happens earlier.
-  content::WindowedNotificationObserver contents_destroyed_observer(
-      content::NOTIFICATION_WEB_CONTENTS_DESTROYED,
-      content::NotificationService::AllSources());
-  contents_destroyed_observer.Wait();
+  // Wait for the actual destruction.
+  destroyed_watcher.Wait();
 
-  // Browser still has the same tab.
-  CheckTitle("no_listeners");
-  EXPECT_EQ(1, browser()->tab_strip_model()->count());
+  // Verify that the destruction had the desired effect.
   EXPECT_EQ("unloaded=ohyeah", GetCookies("no_listeners"));
 }
 
 // Test that fast-tab-close does not break a solo tab.
 IN_PROC_BROWSER_TEST_F(FastUnloadTest, PRE_ClosingLastTabFinishesUnload) {
   // The unload handler sleeps before setting the cookie to catch cases when
   // unload handlers are not allowed to run to completion. (For example,
   // using the detached handler for the tab and then closing the browser.)
   NavigateToPage("unload_sleep_before_cookie");
   EXPECT_EQ(1, browser()->tab_strip_model()->count());
@@ skipping 108 matching lines @@
   content::WindowedNotificationObserver window_observer(
         chrome::NOTIFICATION_BROWSER_CLOSED,
         content::NotificationService::AllSources());
   chrome::CloseWindow(browser());
   CrashTab(beforeunload_contents);
   window_observer.Wait();
 }
 
 // TODO(ojan): Add tests for unload/beforeunload that have multiple tabs
 // and multiple windows.