Fix compile error on clang

ash/desktop_background/desktop_background_widget_controller.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 "ash/desktop_background/desktop_background_widget_controller.h"
 
 #include "ui/aura/root_window.h"
 #include "ui/views/widget/widget.h"
 
 DECLARE_WINDOW_PROPERTY_TYPE(ash::internal::DesktopBackgroundWidgetController*);
@@ skipping 41 matching lines @@
     root_window->GetChildById(src_container)->layer()->Remove(layer);
     root_window->GetChildById(dest_container)->layer()->Add(layer);
   }
 }
 
 ComponentWrapper::ComponentWrapper(
     DesktopBackgroundWidgetController* component) {
   component_.reset(component);
 }
 
+ComponentWrapper::~ComponentWrapper() {
+}
+
 DesktopBackgroundWidgetController* ComponentWrapper::GetComponent(
     bool pass_ownership) {
   if (pass_ownership)
     return component_.release();
   return component_.get();
 }
 
 }  // namespace internal
 }  // namespace ash