Replace network combobox with network dropdown button

chrome/browser/chromeos/login/network_screen_delegate.h

 // Copyright (c) 2010 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.
 
 #ifndef CHROME_BROWSER_CHROMEOS_LOGIN_NETWORK_SCREEN_DELEGATE_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_NETWORK_SCREEN_DELEGATE_H_
 #pragma once
 
 #include "app/combobox_model.h"
 #include "chrome/browser/chromeos/cros/network_library.h"
 #include "views/controls/button/button.h"
 #include "views/controls/combobox/combobox.h"
 
 namespace chromeos {
 
 class LanguageSwitchMenu;
 
 // Interface that NetworkScreen exposes to the NetworkSelectionView.
-class NetworkScreenDelegate : public ComboboxModel,
-                              public views::Combobox::Listener,
-                              public views::ButtonListener,
+class NetworkScreenDelegate : public views::ButtonListener,
                               public NetworkLibrary::Observer {
  public:
   virtual LanguageSwitchMenu* language_switch_menu() = 0;
 
  protected:
   virtual ~NetworkScreenDelegate() {}
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_NETWORK_SCREEN_DELEGATE_H_