Simplify render_process_host_chrome_browsertest.cc

This is a prerequisite for switching WindowedNotificationObserver to use
base::RunLoop instead of deprecated MessageLoopRunner. There were two
nested waits for the same notification which does not make sense and
does not work as is with the upcoming change.

This CL was split out from https://crrev.com/c/982612 and uploaded by
git cl split.

R=jochen@chromium.org

Bug: 668707
Change-Id: I217e5ea431d4a58b15ed1eef51a912142124c8b8
Reviewed-on: https://chromium-review.googlesource.com/1120488Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Commit-Queue: Alexander Semashko <ahest@yandex-team.ru>
Cr-Commit-Position: refs/heads/master@{#572171}

chrome/browser/renderer_host/render_process_host_chrome_browsertest.cc

@@ -527,21 +527,21 @@ IN_PROC_BROWSER_TEST_F(ChromeRenderProcessHostTest,
 class WindowDestroyer : public content::WebContentsObserver {
  public:
   WindowDestroyer(content::WebContents* web_contents, TabStripModel* model)
-      : content::WebContentsObserver(web_contents), tab_strip_model_(model) {}
+      : content::WebContentsObserver(web_contents),
+        tab_strip_model_(model),
+        browser_closed_observer_(chrome::NOTIFICATION_BROWSER_CLOSED,
+                                 content::NotificationService::AllSources()) {}
+
+  // Wait for the browser window to be destroyed.
+  void Wait() { browser_closed_observer_.Wait(); }
 
   void RenderProcessGone(base::TerminationStatus status) override {
-    // Wait for the window to be destroyed, which will ensure all other
-    // RenderViewHost objects are deleted before we return and proceed with
-    // the next iteration of notifications.
-    content::WindowedNotificationObserver observer(
-        chrome::NOTIFICATION_BROWSER_CLOSED,
-        content::NotificationService::AllSources());
     tab_strip_model_->CloseAllTabs();
-    observer.Wait();
   }
 
  private:
   TabStripModel* tab_strip_model_;
+  content::WindowedNotificationObserver browser_closed_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowDestroyer);
 };
@@ -575,16 +575,12 @@ IN_PROC_BROWSER_TEST_F(ChromeRenderProcessHostTest,
   // Create an object that will close the window on a process crash.
   WindowDestroyer destroyer(wc1, browser()->tab_strip_model());
 
-  content::WindowedNotificationObserver observer(
-      chrome::NOTIFICATION_BROWSER_CLOSED,
-      content::NotificationService::AllSources());
-
   // Kill the renderer process, simulating a crash. This should the ProcessDied
   // method to be called. Alternatively, RenderProcessHost::OnChannelError can
   // be called to directly force a call to ProcessDied.
   wc1->GetMainFrame()->GetProcess()->Shutdown(-1);
 
-  observer.Wait();
+  destroyer.Wait();
 }
 
 // Sets up the browser in order to start the tests with two tabs open: one