TaskScheduler: Add delayed run time to the constructor of Task.

base/task_scheduler/task.h

 // Copyright 2016 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_TASK_SCHEDULER_TASK_H_
 #define BASE_TASK_SCHEDULER_TASK_H_
 
 #include "base/base_export.h"
 #include "base/callback_forward.h"
 #include "base/location.h"
 #include "base/pending_task.h"
 #include "base/task_scheduler/task_traits.h"
 #include "base/time/time.h"
 
 namespace base {
 namespace internal {
 
 // A task is a unit of work inside the task scheduler. Support for tracing and
 // profiling inherited from PendingTask.
 struct BASE_EXPORT Task : public PendingTask {
   Task(const tracked_objects::Location& posted_from,

[gab, 2016/04/18 16:20:39]

Also, I don't mind forcing the explicit parameter if you think that's better,
but given only one caller cares about providing this parameter I'd also be fine
with defining a delegated constructor (same as this one minus
|delayed_run_time|) which is delegated as:

Task(const tracked_objects::Location& posted_from, 
     const Closure& task,
     const TaskTraits& traits) 
    : Task(posted_from, task, traits, TimeTicks() {}

[fdoray, 2016/04/18 16:33:44]

I prefer forcing |delayed_run_time| because it is always provided when a Task is
constructed in production (I don't want to add a constructor that will only be
used by tests).

[gab, 2016/04/18 17:00:13]

Good point, hadn't realized all other uses were for tests.

        const Closure& task,
-       const TaskTraits& traits);
+       const TaskTraits& traits,
+       const TimeTicks& delayed_run_time);

[gab, 2016/04/18 16:12:14]

Document parameters (in particular is |delayed_run_time| a delay or the time at
which the delay expires).

[fdoray, 2016/04/18 16:33:44]

Done.

   ~Task();
 
   // The TaskTraits of this task.
   const TaskTraits traits;
 
   // The time at which the task was inserted in its sequence. For an undelayed
   // task, this happens at post time. For a delayed task, this happens some
   // time after the task's delay has expired. If the task hasn't been inserted
   // in a sequence yet, this defaults to a null TimeTicks.
   TimeTicks sequenced_time;
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_TASK_H_