Add trace code to track all posted tasks in message_loop.

base/message_loop.h

Index: base/message_loop.h
diff --git a/base/message_loop.h b/base/message_loop.h
index 67980ead66825ecb3d6b85ca5a8d61034184a72b..fffcd2f47c333cb3da2d4ca2b5d6f96955a40fa5 100644
--- a/base/message_loop.h
+++ b/base/message_loop.h
@@ -430,14 +430,14 @@ class BASE_EXPORT MessageLoop : public base::MessagePump::Delegate {
     // The time when the task should be run.
     base::TimeTicks delayed_run_time;
 
+    // The site this PendingTask was posted from.
+    tracked_objects::Location posted_from;
+
     // 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> {