Fix potential crashes in NetworkHandler code

chromeos/network/network_state_handler.h

Index: chromeos/network/network_state_handler.h
diff --git a/chromeos/network/network_state_handler.h b/chromeos/network/network_state_handler.h
index 2477c1a7a6b71690732674c92fa03f561d367dbc..36db34137a0d2d701694f50de167d3cadeaf2569 100644
--- a/chromeos/network/network_state_handler.h
+++ b/chromeos/network/network_state_handler.h
@@ -81,6 +81,10 @@ class CHROMEOS_EXPORT NetworkStateHandler
 
   ~NetworkStateHandler() override;
 
+  // Called just before destruction to give observers a chance to remove
+  // themselves and disable any networking.
+  void Shutdown();
+
   // Add/remove observers.
   void AddObserver(NetworkStateHandlerObserver* observer,
                    const tracked_objects::Location& from_here);
@@ -374,7 +378,7 @@ class CHROMEOS_EXPORT NetworkStateHandler
   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_;