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

content/browser/renderer_host/render_view_host_manager_browsertest.cc

Index: content/browser/renderer_host/render_view_host_manager_browsertest.cc
diff --git a/content/browser/renderer_host/render_view_host_manager_browsertest.cc b/content/browser/renderer_host/render_view_host_manager_browsertest.cc
index 383ac86a3b0c5deb42656120ddb73d087334a7b5..7213a77be56022c2d06553850b8a9bb824a9a762 100644
--- a/content/browser/renderer_host/render_view_host_manager_browsertest.cc
+++ b/content/browser/renderer_host/render_view_host_manager_browsertest.cc
@@ -319,28 +319,6 @@ IN_PROC_BROWSER_TEST_F(RenderViewHostManagerTest,
   EXPECT_EQ(orig_site_instance, noref_site_instance);
 }
 
-namespace {
-
-class WebContentsDestroyedObserver : public WebContentsObserver {
- public:
-  WebContentsDestroyedObserver(WebContents* web_contents,
-                               const base::Closure& callback)
-      : WebContentsObserver(web_contents),
-        callback_(callback) {
-  }
-
-  virtual void WebContentsDestroyed(WebContents* web_contents) OVERRIDE {
-    callback_.Run();
-  }
-
- private:
-  base::Closure callback_;
-
-  DISALLOW_COPY_AND_ASSIGN(WebContentsDestroyedObserver);
-};
-
-}  // namespace
-
 // Test for crbug.com/116192.  Targeted links should still work after the
 // named target window has swapped processes.
 IN_PROC_BROWSER_TEST_F(RenderViewHostManagerTest,
@@ -411,15 +389,13 @@ IN_PROC_BROWSER_TEST_F(RenderViewHostManagerTest,
   NavigateToURL(new_shell, https_server.GetURL("files/title1.html"));
   EXPECT_EQ(new_site_instance,
             new_shell->web_contents()->GetSiteInstance());
-  scoped_refptr<MessageLoopRunner> loop_runner(new MessageLoopRunner);
-  WebContentsDestroyedObserver close_observer(new_shell->web_contents(),
-                                              loop_runner->QuitClosure());
+  WebContentsDestroyedWatcher close_watcher(new_shell->web_contents());
   EXPECT_TRUE(ExecuteScriptAndExtractBool(
       shell()->web_contents(),
       "window.domAutomationController.send(testCloseWindow());",
       &success));
   EXPECT_TRUE(success);
-  loop_runner->Run();
+  close_watcher.Wait();
 }
 
 // Test that setting the opener to null in a window affects cross-process