Refactor Android's NetworckChangeNotifier.

net/android/network_change_notifier_factory.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 "net/android/network_change_notifier_factory.h"
 
 #include "net/android/network_change_notifier_android.h"
 
 namespace net {
 namespace android {
 
+namespace {
+NetworkChangeNotifier* g_instance = NULL;
+}
+
 NetworkChangeNotifierFactory::NetworkChangeNotifierFactory() {}
 
 net::NetworkChangeNotifier* NetworkChangeNotifierFactory::CreateInstance() {
-  return new NetworkChangeNotifier();
+  DCHECK(!g_instance);
+  g_instance = new NetworkChangeNotifier();
+  return g_instance;
+}
+
+NetworkChangeNotifier* NetworkChangeNotifierFactory::GetInstance() {
+  return g_instance;
 }
 
 }  // namespace android
 }  // namespace net