Use TaskRunner passed in to URLRequestContextBuilder only for the cache

remoting/base/url_request_context_getter.h

 // 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.
 
 #ifndef REMOTING_BASE_URL_REQUEST_CONTEXT_GETTER_H_
 #define REMOTING_BASE_URL_REQUEST_CONTEXT_GETTER_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "net/url_request/url_request_context_getter.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 }  // namespace base
 
 namespace net {
 class NetLog;
 class ProxyConfigService;
 }  // namespace net
 
 namespace remoting {
 
 class URLRequestContextGetter : public net::URLRequestContextGetter {
  public:
+  // TODO(mmenke): Remove |file_task_runner|, as it's no longer used.
   URLRequestContextGetter(
       scoped_refptr<base::SingleThreadTaskRunner> network_task_runner,
       scoped_refptr<base::SingleThreadTaskRunner> file_task_runner);
 
   // Overridden from net::URLRequestContextGetter:
   net::URLRequestContext* GetURLRequestContext() override;
   scoped_refptr<base::SingleThreadTaskRunner> GetNetworkTaskRunner()
       const override;
 
  protected:
   ~URLRequestContextGetter() override;
 
  private:
   scoped_refptr<base::SingleThreadTaskRunner> network_task_runner_;
   scoped_refptr<base::SingleThreadTaskRunner> file_task_runner_;
   std::unique_ptr<net::ProxyConfigService> proxy_config_service_;
   std::unique_ptr<net::NetLog> net_log_;
   std::unique_ptr<net::URLRequestContext> url_request_context_;
 
   DISALLOW_COPY_AND_ASSIGN(URLRequestContextGetter);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_BASE_URL_REQUEST_CONTEXT_GETTER_H_