Remove the dependence on BrowserThread::FILE for

content/shell/browser/shell_url_request_context_getter.cc

Index: content/shell/browser/shell_url_request_context_getter.cc
diff --git a/content/shell/browser/shell_url_request_context_getter.cc b/content/shell/browser/shell_url_request_context_getter.cc
index dcad965c0ff83c59f00a84ea8c18f87d90017a3b..079f23b743e7f535eb1985b10547bcb34cee4cbd 100644
--- a/content/shell/browser/shell_url_request_context_getter.cc
+++ b/content/shell/browser/shell_url_request_context_getter.cc
@@ -95,7 +95,6 @@ ShellURLRequestContextGetter::ShellURLRequestContextGetter(
     : ignore_certificate_errors_(ignore_certificate_errors),
       base_path_(base_path),
       io_task_runner_(std::move(io_task_runner)),
-      file_task_runner_(std::move(file_task_runner)),
       net_log_(net_log),
       request_interceptors_(std::move(request_interceptors)) {
   // Must first be created on the UI thread.
@@ -119,8 +118,7 @@ ShellURLRequestContextGetter::CreateNetworkDelegate() {
 
 std::unique_ptr<net::ProxyConfigService>
 ShellURLRequestContextGetter::GetProxyConfigService() {
-  return net::ProxyService::CreateSystemProxyConfigService(io_task_runner_,
-                                                           file_task_runner_);
+  return net::ProxyService::CreateSystemProxyConfigService(io_task_runner_);
 }
 
 std::unique_ptr<net::ProxyService>