Minor fixes in proxy configuration on iOS.

net/proxy/proxy_config_service_ios.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 NET_PROXY_PROXY_CONFIG_SERVICE_IOS_H_
 #define NET_PROXY_PROXY_CONFIG_SERVICE_IOS_H_
 
 #include "net/proxy/polling_proxy_config_service.h"
 
-namespace base {
-class SingleThreadTaskRunner;
-}  // namespace base
-
 namespace net {
 
 class ProxyConfigServiceIOS : public PollingProxyConfigService {
  public:
   // Constructs a ProxyConfigService that watches the iOS system proxy settings.
-  // This instance is expected to be operated and deleted on the IO thread
-  // (however it may be constructed from a different thread).
-  explicit ProxyConfigServiceIOS(
-      base::SingleThreadTaskRunner* io_thread_task_runner);
+  explicit ProxyConfigServiceIOS();
   virtual ~ProxyConfigServiceIOS();
 
  private:
-  // The thread that we expect to be operated on.
-  scoped_refptr<base::SingleThreadTaskRunner> io_thread_task_runner_;
-
   DISALLOW_COPY_AND_ASSIGN(ProxyConfigServiceIOS);
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_CONFIG_SERVICE_IOS_H_