Hold URLRequestContextGetter by scoped_refptr in Drive related code.

chrome/browser/google_apis/request_sender.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 CHROME_BROWSER_GOOGLE_APIS_REQUEST_SENDER_H_
 #define CHROME_BROWSER_GOOGLE_APIS_REQUEST_SENDER_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 74 matching lines @@
   // Clears any authentication token and retries the request, which forces
   // an authentication token refresh.
   void RetryRequest(AuthenticatedRequestInterface* request);
 
   // Cancels the request. Used for implementing the returned closure of
   // StartRequestWithRetry.
   void CancelRequest(
       const base::WeakPtr<AuthenticatedRequestInterface>& request);
 
   scoped_ptr<AuthServiceInterface> auth_service_;
-  net::URLRequestContextGetter* url_request_context_getter_;  // Not owned.
+  scoped_refptr<net::URLRequestContextGetter> url_request_context_getter_;
   scoped_refptr<base::TaskRunner> blocking_task_runner_;
 
   std::set<AuthenticatedRequestInterface*> in_flight_requests_;
   const std::string custom_user_agent_;
 
   base::ThreadChecker thread_checker_;
 
   // Note: This should remain the last member so it'll be destroyed and
   // invalidate its weak pointers before any other members are destroyed.
   base::WeakPtrFactory<RequestSender> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RequestSender);
 };
 
 }  // namespace google_apis
 
 #endif  // CHROME_BROWSER_GOOGLE_APIS_REQUEST_SENDER_H_