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

ui/views/test/views_test_base.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 "ui/views/test/views_test_base.h"
 
+#include "base/run_loop.h"
+
 #if defined(USE_AURA)
 #include "ui/aura/env.h"
 #include "ui/aura/test/aura_test_helper.h"
 #endif
 
 namespace views {
 
 ViewsTestBase::ViewsTestBase()
     : setup_called_(false),
       teardown_called_(false) {
@@ skipping 23 matching lines @@
   RunPendingMessages();
   teardown_called_ = true;
   views_delegate_.reset();
   testing::Test::TearDown();
 #if defined(USE_AURA)
   aura_test_helper_->TearDown();
 #endif
 }
 
 void ViewsTestBase::RunPendingMessages() {
+  base::RunLoop run_loop;
 #if defined(USE_AURA)
-  message_loop_.RunAllPendingWithDispatcher(
-      aura::Env::GetInstance()->GetDispatcher());
-#else
-  message_loop_.RunAllPending();
+  run_loop.set_dispatcher(aura::Env::GetInstance()->GetDispatcher());
 #endif
+  run_loop.RunUntilIdle();
 }
 
 }  // namespace views