Add queued_time_ms trace for events in message loop

base/tracking_info.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.
 
 // This is a simple struct with tracking information that is stored
 // with a PendingTask (when message_loop is handling the task).
 // Only the information that is shared with the profiler in tracked_objects
 // are included in this structure.
 
 
 #ifndef BASE_TRACKING_INFO_H_
 #define BASE_TRACKING_INFO_H_
 
 #include "base/time/time.h"
 
 namespace tracked_objects {
 class Location;
 class Births;
 }
 
 namespace base {
 
 // This structure is copied around by value.
 struct BASE_EXPORT TrackingInfo {
   TrackingInfo();
   TrackingInfo(const tracked_objects::Location& posted_from,
                base::TimeTicks delayed_run_time);
   ~TrackingInfo();
 
+  // To avoid conflating our stats with the delay duration in a PostDelayedTask,
+  // we identify such tasks, and replace their post_time with the time they
+  // were scheduled (requested?) to emerge from the delayed task queue. This
+  // means that queuing delay for such tasks will show how long they went
+  // unserviced, after they *could* be serviced.  This is the same stat as we
+  // have for non-delayed tasks, and we consistently call it queuing delay.
+  TimeTicks EffectiveTimePosted() const {

[jar (doing other things), 2013/07/09 16:50:53]

Both uses of the return value immediately convert to:

tracked_objects::TrackedTime

You probably should adjust the return value here, and simplify that code.

[Xianzhu, 2013/07/09 17:22:43]

Done.

I thought of consistency with the type of time_posted and delayed_run_time. It's
fine to use TrackedTime as it's only used for tracing/profiling.

+    return delayed_run_time.is_null() ? time_posted : delayed_run_time;
+  }
+
   // Record of location and thread that the task came from.
   tracked_objects::Births* birth_tally;
 
   // Time when the related task was posted.
   base::TimeTicks time_posted;
 
   // The time when the task should be run.
   base::TimeTicks delayed_run_time;
 };
 
 }  // namespace base
 
 #endif  // BASE_TRACKING_INFO_H_