Fix potential crashes in NetworkHandler code

chromeos/network/network_configuration_handler.h

 // 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.
 
 #ifndef CHROMEOS_NETWORK_NETWORK_CONFIGURATION_HANDLER_H_
 #define CHROMEOS_NETWORK_NETWORK_CONFIGURATION_HANDLER_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 187 matching lines @@
   // Signals the device handler to request an IP config refresh.
   void RequestRefreshIPConfigs(const std::string& service_path);
 
   // Unowned associated Network*Handlers (global or test instance).
   NetworkStateHandler* network_state_handler_;
   NetworkDeviceHandler* network_device_handler_;
 
   // Map of in-progress deleter instances. Owned by this class.
   std::map<std::string, ProfileEntryDeleter*> profile_entry_deleters_;
 
-  base::ObserverList<NetworkConfigurationObserver> observers_;
+  base::ObserverList<NetworkConfigurationObserver, true> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkConfigurationHandler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_NETWORK_NETWORK_CONFIGURATION_HANDLER_H_