Initialize the global message center instance to NULL

ui/message_center/message_center.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/message_center/message_center.h"
 
 #include "base/observer_list.h"
 #include "ui/message_center/message_center_impl.h"
 
 namespace message_center {
 
 //------------------------------------------------------------------------------
 
 namespace {
-static MessageCenter* g_message_center;
+static MessageCenter* g_message_center = NULL;
 }
 
 // static
 void MessageCenter::Initialize() {
   DCHECK(g_message_center == NULL);
   g_message_center = new MessageCenterImpl();
 }
 
 // static
 MessageCenter* MessageCenter::Get() {
   DCHECK(g_message_center);
   return g_message_center;
 }
 
 // static
 void MessageCenter::Shutdown() {
   DCHECK(g_message_center);
   delete g_message_center;
   g_message_center = NULL;
 }
 
 MessageCenter::MessageCenter() {
 }
 
 MessageCenter::~MessageCenter() {
 }
 
 }  // namespace message_center