Fix potential crashes in NetworkHandler code

chromeos/network/managed_network_configuration_handler_impl.h

 // Copyright 2013 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_MANAGED_NETWORK_CONFIGURATION_HANDLER_IMPL_H_
 #define CHROMEOS_NETWORK_MANAGED_NETWORK_CONFIGURATION_HANDLER_IMPL_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 197 matching lines @@
   // Owns the currently running PolicyApplicators.
   UserToPolicyApplicatorMap policy_applicators_;
 
   // Per userhash (or empty string for device policy), contains the GUIDs of the
   // policies that were modified.
   // If this map contains a userhash as key, it means that a policy application
   // for this userhash is pending even if no policies were modified and the
   // associated set of GUIDs is empty.
   UserToModifiedPoliciesMap queued_modified_policies_;
 
-  base::ObserverList<NetworkPolicyObserver> observers_;
+  base::ObserverList<NetworkPolicyObserver, true> observers_;
 
   // For Shill client callbacks
   base::WeakPtrFactory<ManagedNetworkConfigurationHandlerImpl>
       weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ManagedNetworkConfigurationHandlerImpl);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_NETWORK_MANAGED_NETWORK_CONFIGURATION_HANDLER_IMPL_H_