Fix network portal detector crash on shutdown

chrome/browser/extensions/api/networking_private/networking_private_chromeos.cc

 // Copyright 2014 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.
 
 #include "chrome/browser/extensions/api/networking_private/networking_private_chromeos.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "chrome/browser/chromeos/profiles/profile_helper.h"
@@ skipping 265 matching lines @@
   NetworkHandler::Get()->network_device_handler()->GetWifiTDLSStatus(
       ip_or_mac_address,
       success_callback,
       base::Bind(&NetworkHandlerFailureCallback, failure_callback));
 }
 
 void NetworkingPrivateChromeOS::GetCaptivePortalStatus(
     const std::string& guid,
     const StringCallback& success_callback,
     const FailureCallback& failure_callback) {
-  chromeos::NetworkPortalDetector* detector =
-      chromeos::NetworkPortalDetector::Get();
-  if (!detector) {
+  if (!chromeos::NetworkPortalDetector::IsInitialized()) {
     failure_callback.Run(networking_private::kErrorNotReady);
     return;
   }
 
   chromeos::NetworkPortalDetector::CaptivePortalState state =
-      detector->GetCaptivePortalState(guid);
+      chromeos::NetworkPortalDetector::Get()->GetCaptivePortalState(guid);
   success_callback.Run(
       chromeos::NetworkPortalDetector::CaptivePortalStatusString(state.status));
 }
 
 scoped_ptr<base::ListValue>
 NetworkingPrivateChromeOS::GetEnabledNetworkTypes() {
   chromeos::NetworkStateHandler* state_handler = GetStateHandler();
 
   scoped_ptr<base::ListValue> network_list(new base::ListValue);
 
@@ skipping 28 matching lines @@
 
   return true;
 }
 
 bool NetworkingPrivateChromeOS::RequestScan() {
   GetStateHandler()->RequestScan();
   return true;
 }
 
 }  // namespace extensions