Introduce task_runner() accessors for both base::Thread and base::MessageLoop

base/threading/thread.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_THREADING_THREAD_H_
 #define BASE_THREADING_THREAD_H_
 
 #include <string>
 
 #include "base/base_export.h"
@@ skipping 120 matching lines @@
   // Returns the message loop for this thread.  Use the MessageLoop's
   // PostTask methods to execute code on the thread.  This only returns
   // non-null after a successful call to Start.  After Stop has been called,
   // this will return NULL.
   //
   // NOTE: You must not call this MessageLoop's Quit method directly.  Use
   // the Thread's Stop method instead.
   //
   MessageLoop* message_loop() const { return message_loop_; }
 
-  // Returns a MessageLoopProxy for this thread.  Use the MessageLoopProxy's
-  // PostTask methods to execute code on the thread.  This only returns
-  // non-NULL after a successful call to Start. After Stop has been called,
-  // this will return NULL. Callers can hold on to this even after the thread
-  // is gone.
+  // Returns a MessageLoopProxy for this thread. Use the MessageLoopProxy's
+  // PostTask methods to execute code on the thread. Returns NULL if the thread
+  // is not running (e.g. before Start or after Stop have been called). Callers
+  // can hold on to this even after the thread is gone; in this situation,
+  // attempts to PostTask() will fail.
+  //
+  // Note: This method is deprecated. Callers should call task_runner() instead
+  // and use the TaskRunner interfaces for safely interfacing with the Thread.
   scoped_refptr<MessageLoopProxy> message_loop_proxy() const {
     return message_loop_ ? message_loop_->message_loop_proxy() : NULL;
   }
 
+  // Returns a TaskRunner for this thread. Use the TaskRunner's PostTask
+  // methods to execute code on the thread. Returns NULL if the thread is not
+  // running (e.g. before Start or after Stop have been called). Callers can
+  // hold on to this even after the thread is gone; in this situation, attempts
+  // to PostTask() will fail.
+  scoped_refptr<SingleThreadTaskRunner> task_runner() const {
+    return message_loop_proxy();
+  }
+
   // Returns the name of this thread (for display in debugger too).
   const std::string& thread_name() const { return name_; }
 
   // The native thread handle.
   PlatformThreadHandle thread_handle() { return thread_; }
 
   // The thread ID.
   PlatformThreadId thread_id() const { return thread_id_; }
 
   // Returns true if the thread has been started, and not yet stopped.
@@ skipping 64 matching lines @@
   std::string name_;
 
   friend void ThreadQuitHelper();
 
   DISALLOW_COPY_AND_ASSIGN(Thread);
 };
 
 }  // namespace base
 
 #endif  // BASE_THREADING_THREAD_H_