[UI Views] Don't allow a ButtonListener and a MenuButtonListener

ui/message_center/views/notifier_settings_view.cc

 // Copyright (c) 2013 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/message_center/views/notifier_settings_view.h"
 
 #include <stddef.h>
 
 #include <set>
 #include <string>
@@ skipping 560 matching lines @@
       settings::kTitleMargin + kMenuButtonInnateMargin,
       0,
       settings::kTitleMargin + kMenuButtonInnateMargin));
   contents_title_view->AddChildView(top_label);
 
   if (need_account_switcher) {
     const NotifierGroup& active_group = provider_->GetActiveNotifierGroup();
     base::string16 notifier_group_text = active_group.login_info.empty() ?
         active_group.name : active_group.login_info;
     notifier_group_selector_ =
-        new views::MenuButton(NULL, notifier_group_text, this, true);
+        new views::MenuButton(notifier_group_text, this, true);
     notifier_group_selector_->SetBorder(scoped_ptr<views::Border>(
         new views::LabelButtonAssetBorder(views::Button::STYLE_BUTTON)));
     notifier_group_selector_->SetFocusPainter(nullptr);
     notifier_group_selector_->set_animate_on_state_change(false);
     notifier_group_selector_->SetFocusable(true);
     contents_title_view->AddChildView(notifier_group_selector_);
   }
 
   contents_view->AddChildView(contents_title_view);
 
@@ skipping 108 matching lines @@
                                              notifier_group_selector_,
                                              menu_anchor,
                                              views::MENU_ANCHOR_BUBBLE_ABOVE,
                                              ui::MENU_SOURCE_MOUSE))
     return;
   MessageCenterView* center_view = static_cast<MessageCenterView*>(parent());
   center_view->OnSettingsChanged();
 }
 
 }  // namespace message_center