Fix potential crashes in NetworkHandler code

chromeos/network/network_state_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_STATE_HANDLER_H_
 #define CHROMEOS_NETWORK_NETWORK_STATE_HANDLER_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 356 matching lines @@
   std::string GetTechnologyForType(const NetworkTypePattern& type) const;
 
   // Returns all the technology types for |type|.
   ScopedVector<std::string> GetTechnologiesForType(
       const NetworkTypePattern& type) const;
 
   // Shill property handler instance, owned by this class.
   scoped_ptr<internal::ShillPropertyHandler> shill_property_handler_;
 
   // Observer list
-  base::ObserverList<NetworkStateHandlerObserver> observers_;
+  base::ObserverList<NetworkStateHandlerObserver, true> observers_;
 
   // List of managed network states
   ManagedStateList network_list_;
 
   // Set to true when the network list is sorted, cleared when network updates
   // arrive. Used to trigger sorting when needed.
   bool network_list_sorted_;
 
   // List of managed device states
   ManagedStateList device_list_;
 
   // Keeps track of the default network for notifying observers when it changes.
   std::string default_network_path_;
 
   // List of interfaces on which portal check is enabled.
   std::string check_portal_list_;
 
   // Map of network specifiers to guids. Contains an entry for each
   // NetworkState that is not saved in a profile.
   SpecifierGuidMap specifier_guid_map_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkStateHandler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_NETWORK_NETWORK_STATE_HANDLER_H_