MessageLoop's RUN method will pass a const ref to PendingTask when

base/message_loop.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_H_
 #define BASE_MESSAGE_LOOP_H_
 
 #include <queue>
 #include <string>
 
@@ skipping 321 matching lines @@
 
   // A TaskObserver is an object that receives task notifications from the
   // MessageLoop.
   //
   // NOTE: A TaskObserver implementation should be extremely fast!
   class BASE_EXPORT TaskObserver {
    public:
     TaskObserver();
 
     // This method is called before processing a task.
-    virtual void WillProcessTask(base::TimeTicks time_posted) = 0;
+    virtual void WillProcessTask(const base::PendingTask& pending_task) = 0;
 
     // This method is called after processing a task.
-    virtual void DidProcessTask(base::TimeTicks time_posted) = 0;
+    virtual void DidProcessTask(const base::PendingTask& pending_task) = 0;
 
    protected:
     virtual ~TaskObserver();
   };
 
   // These functions can only be called on the same thread that |this| is
   // running on.
   void AddTaskObserver(TaskObserver* task_observer);
   void RemoveTaskObserver(TaskObserver* task_observer);
 
@@ skipping 343 matching lines @@
 #endif  // defined(OS_POSIX)
 };
 
 // Do not add any member variables to MessageLoopForIO!  This is important b/c
 // MessageLoopForIO is often allocated via MessageLoop(TYPE_IO).  Any extra
 // data that you need should be stored on the MessageLoop's pump_ instance.
 COMPILE_ASSERT(sizeof(MessageLoop) == sizeof(MessageLoopForIO),
                MessageLoopForIO_should_not_have_extra_member_variables);
 
 #endif  // BASE_MESSAGE_LOOP_H_