Make aura::clients take Window instead of RootWindow

ui/aura/client/event_client.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 "ui/aura/client/event_client.h"
 
 #include "ui/aura/root_window.h"
 #include "ui/aura/window_property.h"
 
 DECLARE_WINDOW_PROPERTY_TYPE(aura::client::EventClient*)
 
 namespace aura {
 namespace client {
 
 DEFINE_WINDOW_PROPERTY_KEY(EventClient*, kRootWindowEventClientKey, NULL);
 
-void SetEventClient(RootWindow* root_window, EventClient* client) {
+void SetEventClient(Window* root_window, EventClient* client) {
+  DCHECK_EQ(root_window->GetRootWindow(), root_window);
   root_window->SetProperty(kRootWindowEventClientKey, client);
 }
 
-EventClient* GetEventClient(const RootWindow* root_window) {
+EventClient* GetEventClient(const Window* root_window) {
+  if (root_window)
+    DCHECK_EQ(root_window->GetRootWindow(), root_window);
   return root_window ?
       root_window->GetProperty(kRootWindowEventClientKey) : NULL;
 }
 
 }  // namespace client
 }  // namespace aura