Remove the dependence on BrowserThread::FILE for

headless/lib/browser/headless_url_request_context_getter.cc

 // Copyright 2016 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 "headless/lib/browser/headless_url_request_context_getter.h"
 
 #include <memory>
 #include <utility>
 #include <vector>
 
@@ skipping 33 matching lines @@
     protocol_handlers_[pair.first] =
         linked_ptr<net::URLRequestJobFactory::ProtocolHandler>(
             pair.second.release());
   }
   context_protocol_handlers.clear();
 
   // We must create the proxy config service on the UI loop on Linux because it
   // must synchronously run on the glib message loop. This will be passed to
   // the URLRequestContextStorage on the IO thread in GetURLRequestContext().
   if (proxy_server_.IsEmpty()) {
-    proxy_config_service_ = net::ProxyService::CreateSystemProxyConfigService(
-        io_task_runner_, file_task_runner_);
+    proxy_config_service_ =
+        net::ProxyService::CreateSystemProxyConfigService(io_task_runner_);
   }
 }
 
 HeadlessURLRequestContextGetter::~HeadlessURLRequestContextGetter() {}
 
 net::URLRequestContext*
 HeadlessURLRequestContextGetter::GetURLRequestContext() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
   if (!url_request_context_) {
     net::URLRequestContextBuilder builder;
@@ skipping 37 matching lines @@
 scoped_refptr<base::SingleThreadTaskRunner>
 HeadlessURLRequestContextGetter::GetNetworkTaskRunner() const {
   return io_task_runner_;
 }
 
 net::HostResolver* HeadlessURLRequestContextGetter::host_resolver() const {
   return url_request_context_->host_resolver();
 }
 
 }  // namespace headless