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

chrome/test/base/testing_profile.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 "chrome/test/base/testing_profile.h"
 
 #include "build/build_config.h"
 
 #include "base/base_paths.h"
 #include "base/command_line.h"
@@ skipping 360 matching lines @@
 
 void TestingProfile::CreateWebDataService() {
   WebDataServiceFactory::GetInstance()->SetTestingFactory(
       this, BuildWebDataService);
 }
 
 void TestingProfile::BlockUntilBookmarkModelLoaded() {
   DCHECK(GetBookmarkModel());
   if (GetBookmarkModel()->IsLoaded())
     return;
-  BookmarkLoadObserver observer;
+  MessageLoop::RunLoop run_loop;
+  BookmarkLoadObserver observer(run_loop.AsWeakPtr());
   GetBookmarkModel()->AddObserver(&observer);
-  MessageLoop::current()->Run();
+  run_loop.Run();
   GetBookmarkModel()->RemoveObserver(&observer);
   DCHECK(GetBookmarkModel()->IsLoaded());
 }
 
 // TODO(phajdan.jr): Doesn't this hang if Top Sites are already loaded?
 void TestingProfile::BlockUntilTopSitesLoaded() {
   ui_test_utils::WindowedNotificationObserver top_sites_loaded_observer(
       chrome::NOTIFICATION_TOP_SITES_LOADED,
       content::NotificationService::AllSources());
   if (!GetHistoryService(Profile::EXPLICIT_ACCESS))
@@ skipping 318 matching lines @@
 }
 
 bool TestingProfile::WasCreatedByVersionOrLater(const std::string& version) {
   return true;
 }
 
 base::Callback<ChromeURLDataManagerBackend*(void)>
     TestingProfile::GetChromeURLDataManagerBackendGetter() const {
   return base::Callback<ChromeURLDataManagerBackend*(void)>();
 }