Add base::RunLoop and update ui_test_utils to use it to reduce flakiness

chrome/browser/tab_contents/render_view_context_menu_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 <string>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/string16.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/app/chrome_command_ids.h"
@@ skipping 83 matching lines @@
 // GTK requires a X11-level mouse event to open a context menu correctly.
 #if defined(TOOLKIT_GTK)
 #define MAYBE_RealMenu DISABLED_RealMenu
 #else
 #define MAYBE_RealMenu RealMenu
 #endif
 // Opens a link in a new tab via a "real" context menu.
 IN_PROC_BROWSER_TEST_F(ContextMenuBrowserTest,
                        MAYBE_RealMenu) {
   ContextMenuNotificationObserver menu_observer(
-      IDC_CONTENT_CONTEXT_OPENLINKNEWTAB,
-      chrome::NOTIFICATION_TAB_ADDED);
+      IDC_CONTENT_CONTEXT_OPENLINKNEWTAB);
   ui_test_utils::WindowedTabAddedNotificationObserver tab_observer(
       content::NotificationService::AllSources());
 
   // Go to a page with a link
   ui_test_utils::NavigateToURL(
       browser(), GURL("data:text/html,<a href='about:blank'>link</a>"));
 
   // Open a context menu.
   WebKit::WebMouseEvent mouse_event;
   mouse_event.type = WebKit::WebInputEvent::MouseDown;
@@ skipping 14 matching lines @@
   // be added.
   tab_observer.Wait();
   tab = tab_observer.GetTab();
   ui_test_utils::WaitForLoadStop(tab);
 
   // Verify that it's the correct tab.
   EXPECT_EQ(GURL("about:blank"), tab->GetURL());
 }
 
 }  // namespace