views: Factor out Listener from Combobox into its own header file.

views/controls/combobox/combobox.cc

 // Copyright (c) 2011 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 "views/controls/combobox/combobox.h"
 
 #include "base/logging.h"
 #include "base/utf_string_conversions.h"
 #include "ui/base/accessibility/accessible_view_state.h"
 #include "ui/base/keycodes/keyboard_codes.h"
 #include "ui/base/models/combobox_model.h"
+#include "views/controls/combobox/combobox_listener.h"
 #include "views/controls/native/native_view_host.h"
 #include "views/widget/widget.h"
 
 namespace views {
 
 // static
 const char Combobox::kViewClassName[] = "views/Combobox";
 
 ////////////////////////////////////////////////////////////////////////////////
 // Combobox, public:
@@ skipping 111 matching lines @@
     native_wrapper_ = NativeComboboxWrapper::CreateWrapper(this);
     AddChildView(native_wrapper_->GetView());
   }
 }
 
 std::string Combobox::GetClassName() const {
   return kViewClassName;
 }
 
 }  // namespace views