[Win] Battery Status API: use SingletonHwnd for notifications.

ui/gfx/win/singleton_hwnd.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/gfx/win/singleton_hwnd.h"
 
 #include "base/memory/singleton.h"
 #include "base/message_loop/message_loop.h"
 
 namespace gfx {
 
 // static
 SingletonHwnd* SingletonHwnd::GetInstance() {
   return Singleton<SingletonHwnd>::get();
 }
 
 void SingletonHwnd::AddObserver(Observer* observer) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   observer_list_.AddObserver(observer);
 }
 
 void SingletonHwnd::RemoveObserver(Observer* observer) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   if (!hwnd())
     return;
   observer_list_.RemoveObserver(observer);
 }
 
 BOOL SingletonHwnd::ProcessWindowMessage(HWND window,
                                          UINT message,
                                          WPARAM wparam,
                                          LPARAM lparam,
                                          LRESULT& result,
                                          DWORD msg_map_id) {
   FOR_EACH_OBSERVER(Observer,
                     observer_list_,
                     OnWndProc(window, message, wparam, lparam));
   return false;
 }
 
 SingletonHwnd::SingletonHwnd() {
+  DCHECK(thread_checker_.CalledOnValidThread());
   if (!base::MessageLoopForUI::IsCurrent()) {
     // Creating this window in (e.g.) a renderer inhibits shutdown on
     // Windows. See http://crbug.com/230122 and http://crbug.com/236039.
-    DLOG(ERROR) << "Cannot create windows on non-UI thread!";
+    DLOG(FATAL) << "Cannot create windows on non-UI thread!";
     return;
   }
   WindowImpl::Init(NULL, Rect());
 }
 
 SingletonHwnd::~SingletonHwnd() {
 }
 
 }  // namespace gfx