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 69 matching lines @@
 class QuittingHistoryDBTask : public HistoryDBTask {
  public:
   QuittingHistoryDBTask() {}
 
   virtual bool RunOnDBThread(history::HistoryBackend* backend,
                              history::HistoryDatabase* db) {
     return true;
   }
 
   virtual void DoneRunOnMainThread() {
-    MessageLoop::current()->Quit();
+    MessageLoop::current()->QuitNow();
   }
 
  private:
   ~QuittingHistoryDBTask() {}
 
   DISALLOW_COPY_AND_ASSIGN(QuittingHistoryDBTask);
 };
 
 class TestExtensionURLRequestContext : public net::URLRequestContext {
  public:
@@ skipping 611 matching lines @@
 }
 
 bool TestingProfile::WasCreatedByVersionOrLater(const std::string& version) {
   return true;
 }
 
 base::Callback<ChromeURLDataManagerBackend*(void)>
     TestingProfile::GetChromeURLDataManagerBackendGetter() const {
   return base::Callback<ChromeURLDataManagerBackend*(void)>();
 }