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..260ea699b095fadf25e28f6a266d5b678dd5e5ee 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;

[joth, 2011/09/15 10:38:09]

I managed to avoid this one by using post_births->location() (but, bearing in
mind post_births maybe NULL esp early in startup)

This does make it limited to TRACK_ALL_TASK_OBJECTS builds though, but that
seemed a reasonable trade off?

[jbates, 2011/09/15 16:48:33]

Are we talking about a memory tradeoff? I actually don't think adding two
pointers to PendingTask significantly effects memory usage. These objects
typically only exist while a task is pending. The advantage of being able to
trace tasks in the field will be invaluable, since we often ask reporters of
bugs to run traces while reproducing a bug.

+
     // 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> {