Reland: Explicitly track the scheduler task enqueueing order in a new field

components/scheduler/child/task_queue_manager.h

 // Copyright 2014 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 CONTENT_RENDERER_SCHEDULER_TASK_QUEUE_MANAGER_H_
 #define CONTENT_RENDERER_SCHEDULER_TASK_QUEUE_MANAGER_H_
 
 #include <map>
 
 #include "base/atomic_sequence_num.h"
@@ skipping 13 matching lines @@
 
 namespace trace_event {
 class ConvertableToTraceFormat;
 class TracedValue;
 }  // namespace trace_event
 }  // namespace base
 
 namespace scheduler {
 namespace internal {
 class LazyNow;
+struct SchedulerTask;
 class TaskQueueImpl;
 }  // namespace internal
 
 class NestableSingleThreadTaskRunner;
 
 // The task queue manager provides N task queues and a selector interface for
 // choosing which task queue to service next. Each task queue consists of two
 // sub queues:
 //
 // 1. Incoming task queue. Tasks that are posted get immediately appended here.
@@ skipping 52 matching lines @@
   class DeletionSentinel : public base::RefCounted<DeletionSentinel> {
    private:
     friend class base::RefCounted<DeletionSentinel>;
     ~DeletionSentinel() {}
   };
 
   // TaskQueueSelector::Observer implementation:
   void OnTaskQueueEnabled() override;
 
   // Called by the task queue to register a new pending task.
-  void DidQueueTask(const base::PendingTask& pending_task);
+  void DidQueueTask(internal::SchedulerTask& pending_task);

[Sami, 2015/08/05 11:27:34]

The argument should be a pointer since we're modifying it.

[alex clarke (OOO till 29th), 2015/08/05 14:32:44]

Done.

 
   // Post a task to call DoWork() on the main task runner.  Only one pending
   // DoWork is allowed from the main thread, to prevent an explosion of pending
   // DoWorks.
   void MaybePostDoWorkOnMainRunner();
 
   // Use the selector to choose a pending task and run it.
   void DoWork(bool posted_from_main_thread);
 
   // Delayed Tasks with run_times <= Now() are enqueued onto the work queue.
   // Reloads any empty work queues which have automatic pumping enabled and
   // which are eligible to be auto pumped based on the |previous_task| which was
   // run and |should_trigger_wakeup|. Call with an empty |previous_task| if no
   // task was just run.
   void UpdateWorkQueues(bool should_trigger_wakeup,
-                        const base::PendingTask* previous_task);
+                        const internal::SchedulerTask* previous_task);
 
   // Chooses the next work queue to service. Returns true if |out_queue|
   // indicates the queue from which the next task should be run, false to
   // avoid running any tasks.
   bool SelectQueueToService(internal::TaskQueueImpl** out_queue);
 
   // Runs a single nestable task from the |queue|. On exit, |out_task| will
   // contain the task which was executed. Non-nestable task are reposted on the
   // run loop. The queue must not be empty. Returns true if the TaskQueueManager
   // got deleted, and false otherwise.
   bool ProcessTaskFromWorkQueue(internal::TaskQueueImpl* queue,
-                                base::PendingTask* out_previous_task);
+                                internal::SchedulerTask* out_previous_task);
 
   bool RunsTasksOnCurrentThread() const;
   bool PostDelayedTask(const tracked_objects::Location& from_here,
                        const base::Closure& task,
                        base::TimeDelta delay);
   bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
                                   const base::Closure& task,
                                   base::TimeDelta delay);
 
   base::TimeTicks Now() const;
 
   int GetNextSequenceNumber();
+  int GetNextAgeNumber();
 
   scoped_refptr<base::trace_event::ConvertableToTraceFormat>
   AsValueWithSelectorResult(bool should_run,
                             internal::TaskQueueImpl* selected_queue) const;
 
   // Causes DoWork to start calling UpdateWorkQueue for |queue|. Can be called
   // from any thread.
   void RegisterAsUpdatableTaskQueue(internal::TaskQueueImpl* queue);
 
   // Prevents DoWork from calling UpdateWorkQueue for |queue|. Must be called
   // from the thread the TaskQueueManager was created on.
   void UnregisterAsUpdatableTaskQueue(internal::TaskQueueImpl* queue);
 
   std::set<scoped_refptr<internal::TaskQueueImpl>> queues_;
 
   // This lock guards only |newly_updatable_|.  It's not expected to be heavily
   // contended.
   base::Lock newly_updatable_lock_;
   std::vector<internal::TaskQueueImpl*> newly_updatable_;
 
   // Set of task queues with avaliable work on the incoming queue.  This should
   // only be accessed from the main thread.
   std::set<internal::TaskQueueImpl*> updatable_queue_set_;
 
   base::AtomicSequenceNumber task_sequence_num_;
+  base::AtomicSequenceNumber task_age_num_;
   base::debug::TaskAnnotator task_annotator_;
 
   base::ThreadChecker main_thread_checker_;
   scoped_refptr<NestableSingleThreadTaskRunner> main_task_runner_;
   internal::TaskQueueSelector selector_;
 
   base::Closure do_work_from_main_thread_closure_;
   base::Closure do_work_from_other_thread_closure_;
 
   bool task_was_run_on_quiescence_monitored_queue_;
@@ skipping 13 matching lines @@
 
   scoped_refptr<DeletionSentinel> deletion_sentinel_;
   base::WeakPtrFactory<TaskQueueManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TaskQueueManager);
 };
 
 }  // namespace scheduler
 
 #endif  // CONTENT_RENDERER_SCHEDULER_TASK_QUEUE_MANAGER_H_