Use SequencedTaskRunner rather than SingledThreadedTaskRunner for passing io_task_runner

net/proxy/proxy_config_service_linux.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_LINUX_H_
 #define NET_PROXY_PROXY_CONFIG_SERVICE_LINUX_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 167 matching lines @@
 
     // Synchronously obtains the proxy configuration. If gconf,
     // gsettings, or kioslaverc are used, also enables notifications for
     // setting changes. gconf/gsettings must only be accessed from the
     // thread running the default glib main loop, and so this method
     // must be called from the UI thread. The message loop for the IO
     // thread is specified so that notifications can post tasks to it
     // (and for assertions).
     void SetUpAndFetchInitialConfig(
         const scoped_refptr<base::SingleThreadTaskRunner>& glib_task_runner,
-        const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner);
+        const scoped_refptr<base::SequencedTaskRunner>& io_task_runner);
 
     // Handler for setting change notifications: fetches a new proxy
     // configuration from settings, and if this config is different
     // than what we had before, posts a task to have it stored in
     // cached_config_.
     // Left public for simplicity.
     void OnCheckProxyConfigSettings();
 
     // Called from IO thread.
     void AddObserver(Observer* observer);
@@ skipping 61 matching lines @@
     // base/message_loop/message_pump_glib.h). It is the glib default loop in
     // the sense that it runs the glib default context: as in the context where
     // sources are added by g_timeout_add and g_idle_add, and returned by
     // g_main_context_default. gconf uses glib timeouts and idles and possibly
     // other callbacks that will all be dispatched on this thread. Since gconf
     // is not thread safe, any use of gconf must be done on the thread running
     // this loop.
     scoped_refptr<base::SingleThreadTaskRunner> glib_task_runner_;
     // Task runner for the IO thread. GetLatestProxyConfig() is called from
     // the thread running this loop.
-    scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
+    scoped_refptr<base::SequencedTaskRunner> io_task_runner_;
 
     base::ObserverList<Observer> observers_;
 
     DISALLOW_COPY_AND_ASSIGN(Delegate);
   };
 
   // Thin wrapper shell around Delegate.
 
   // Usual constructor
   ProxyConfigServiceLinux();
 
   // For testing: take alternate setting and env var getter implementations.
   explicit ProxyConfigServiceLinux(
       std::unique_ptr<base::Environment> env_var_getter);
   ProxyConfigServiceLinux(std::unique_ptr<base::Environment> env_var_getter,
                           SettingGetter* setting_getter);
 
   ~ProxyConfigServiceLinux() override;
 
   void SetupAndFetchInitialConfig(
       const scoped_refptr<base::SingleThreadTaskRunner>& glib_task_runner,
-      const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner) {
+      const scoped_refptr<base::SequencedTaskRunner>& io_task_runner) {
     delegate_->SetUpAndFetchInitialConfig(glib_task_runner, io_task_runner);
   }
   void OnCheckProxyConfigSettings() {
     delegate_->OnCheckProxyConfigSettings();
   }
 
   // ProxyConfigService methods:
   // Called from IO thread.
   void AddObserver(Observer* observer) override;
   void RemoveObserver(Observer* observer) override;
   ProxyConfigService::ConfigAvailability GetLatestProxyConfig(
       ProxyConfig* config) override;
 
  private:
   scoped_refptr<Delegate> delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(ProxyConfigServiceLinux);
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_CONFIG_SERVICE_LINUX_H_