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

chrome/browser/ui/views/toolbar/chevron_menu_button.cc

 // Copyright 2014 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/toolbar/chevron_menu_button.h"
 
 #include <stddef.h>
 
 #include "base/location.h"
 #include "base/macros.h"
@@ skipping 343 matching lines @@
 
 size_t ChevronMenuButton::MenuController::IndexForId(int id) const {
   // The index of the view being dragged (GetCommand gives a 1-based index into
   // the overflow menu).
   DCHECK_GT(browser_actions_container_->VisibleBrowserActions() + id, 0u);
   return browser_actions_container_->VisibleBrowserActions() + id - 1;
 }
 
 ChevronMenuButton::ChevronMenuButton(
     BrowserActionsContainer* browser_actions_container)
-    : views::MenuButton(NULL, base::string16(), this, false),
+    : views::MenuButton(base::string16(), this, false),
       browser_actions_container_(browser_actions_container),
       weak_factory_(this) {
   // Set the border explicitly, because otherwise the native theme manager takes
   // over and reassigns the insets we set in CreateDefaultBorder().
   SetBorder(CreateDefaultBorder());
 }
 
 ChevronMenuButton::~ChevronMenuButton() {
 }
 
@@ skipping 65 matching lines @@
   // We should never try to show an overflow menu when one is already visible.
   DCHECK(!menu_controller_);
   menu_controller_.reset(new MenuController(
       this, browser_actions_container_, for_drop));
   menu_controller_->RunMenu(GetWidget());
 }
 
 void ChevronMenuButton::MenuDone() {
   menu_controller_.reset();
 }