Fix potential crashes in NetworkHandler code

chromeos/network/network_state_handler_observer.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_OBSERVER_H_
 #define CHROMEOS_NETWORK_NETWORK_STATE_HANDLER_OBSERVER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 35 matching lines @@
   virtual void NetworkPropertiesUpdated(const NetworkState* network);
 
   // One or more properties of |device| have been updated.
   virtual void DevicePropertiesUpdated(const DeviceState* device);
 
   // A scan for |device| completed.
   virtual void ScanCompleted(const DeviceState* device);
 
   // Called just before NetworkStateHandler is destroyed so that observers
   // can safely stop observing.
-  virtual void IsShuttingDown();
+  virtual void OnShuttingDown();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(NetworkStateHandlerObserver);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_NETWORK_NETWORK_STATE_HANDLER_OBSERVER_H_