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 601120fe99aa8d211348d88bec4bfd272e442cc2..cbbda7ed93085bc0f83895a3e7afb8f10c64246b 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 birth_location;

[jbates, 2011/08/31 00:40:48]

Location is only three pointers, so if we store the whole thing here we know
what code posted tasks that show up in traces. (Also moved it up here to reduce
struct padding.)

[darin (slow to review), 2011/08/31 21:40:55]

So post_births has this same information:  post_births->location()

It seems like we should somehow rectify these two uses of location tracking. 
You should really discuss this with Jar since he created the tracked object
system.

+
     // 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> {