base: Make it possible to replace the MessageLoop's task runner

base/message_loop/message_loop_task_runner.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 BASE_MESSAGE_LOOP_MESSAGE_LOOP_TASK_RUNNER_H_
 #define BASE_MESSAGE_LOOP_MESSAGE_LOOP_TASK_RUNNER_H_
 
 #include "base/base_export.h"
 #include "base/memory/ref_counted.h"
+#include "base/message_loop/bindable_single_thread_task_runner.h"
 #include "base/pending_task.h"
-#include "base/single_thread_task_runner.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/platform_thread.h"
 
 namespace base {
 namespace internal {
 
 class IncomingTaskQueue;
 
-// A stock implementation of SingleThreadTaskRunner that is created and managed
-// by a MessageLoop. For now a MessageLoopTaskRunner can only be created as
-// part of a MessageLoop.
-class BASE_EXPORT MessageLoopTaskRunner : public SingleThreadTaskRunner {
+// A stock implementation of BindableSingleThreadTaskRunner that is created and
+// managed by a MessageLoop. For now a MessageLoopTaskRunner can only be
+// created as part of a MessageLoop.
+class BASE_EXPORT MessageLoopTaskRunner
+    : public BindableSingleThreadTaskRunner {
  public:
   explicit MessageLoopTaskRunner(
       scoped_refptr<IncomingTaskQueue> incoming_queue);
 
-  // Initialize this message loop task runner on the current thread.
-  void BindToCurrentThread();
-
-  // SingleThreadTaskRunner implementation
+  // BindableSingleThreadTaskRunner implementation
+  void BindToCurrentThread() override;
   bool PostDelayedTask(const tracked_objects::Location& from_here,
                        const base::Closure& task,
                        base::TimeDelta delay) override;
   bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
                                   const base::Closure& task,
                                   base::TimeDelta delay) override;
   bool RunsTasksOnCurrentThread() const override;
 
  private:
   friend class RefCountedThreadSafe<MessageLoopTaskRunner>;
   ~MessageLoopTaskRunner() override;
 
   // The incoming queue receiving all posted tasks.
   scoped_refptr<IncomingTaskQueue> incoming_queue_;
 
   // ID of the thread |this| was created on.  Could be accessed on multiple
   // threads, protected by |valid_thread_id_lock_|.
   PlatformThreadId valid_thread_id_;
   mutable Lock valid_thread_id_lock_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageLoopTaskRunner);
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_MESSAGE_LOOP_MESSAGE_LOOP_TASK_RUNNER_H_