Tag all tracked objects, including Tasks, with the program counter at the site of FROM_HERE.

base/message_loop.h

 // Copyright (c) 2011 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_
 #pragma once
 
 #include <queue>
 #include <string>
@@ skipping 397 matching lines @@
     base::TimeTicks time_posted;
 
     // The time when the task should be run.
     base::TimeTicks delayed_run_time;
 
     // Secondary sort key for run time.
     int sequence_num;
 
     // OK to dispatch from a nested loop.
     bool nestable;
+
+    // The site this PendingTask was posted from.
+    const void* birth_program_counter;
   };
 
   class TaskQueue : public std::queue<PendingTask> {
    public:
     void Swap(TaskQueue* queue) {
       c.swap(queue->c);  // Calls std::deque::swap
     }
   };
 
   typedef std::priority_queue<PendingTask> DelayedTaskQueue;
@@ skipping 259 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_