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

chrome/browser/ui/views/user_data_dir_dialog_view.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/browser/ui/views/user_data_dir_dialog_view.h"
 
 #include "base/logging.h"
+#include "base/run_loop.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/ui/user_data_dir_dialog.h"
 #include "grit/chromium_strings.h"
 #include "grit/generated_resources.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/views/controls/message_box_view.h"
 #include "ui/views/widget/widget.h"
 
 UserDataDirDialogView::UserDataDirDialogView(const FilePath& user_data_dir)
     : ALLOW_THIS_IN_INITIALIZER_LIST(
@@ skipping 75 matching lines @@
   user_data_dir_ = path;
   is_blocking_ = false;
 }
 
 void UserDataDirDialogView::FileSelectionCanceled(void* params) {
 }
 
 namespace browser {
 
 FilePath ShowUserDataDirDialog(const FilePath& user_data_dir) {
+  DCHECK_EQ(MessageLoop::TYPE_UI, MessageLoop::current()->type());
   // When the window closes, it will delete itself.
   UserDataDirDialogView* dialog = new UserDataDirDialogView(user_data_dir);
   views::Widget::CreateWindow(dialog)->Show();
-  MessageLoopForUI::current()->RunWithDispatcher(dialog);
+  base::RunLoop run_loop(dialog);
+  run_loop.Run();
   return dialog->user_data_dir();
 }
 
 }  // namespace browser