scheduler: Ensure consistent delayed task ordering between task queues

third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h

 // Copyright 2015 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 THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_TASK_QUEUE_IMPL_H_
 #define THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_TASK_QUEUE_IMPL_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 159 matching lines @@
 
   const WorkQueue* immediate_work_queue() const {
     return main_thread_only().immediate_work_queue.get();
   }
 
   bool should_report_when_execution_blocked() const {
     return should_report_when_execution_blocked_;
   }
 
   // Enqueues any delayed tasks which should be run now on the
-  // |delayed_work_queue|. Returns the deadline if a subsequent wakeup is
-  // required. Must be called from the main thread.
-  base::Optional<base::TimeTicks> WakeUpForDelayedWork(LazyNow* lazy_now);
+  // |delayed_work_queue|. Returns true and fills |out_next_wake_up_time| and
+  // |out_next_wake_up_sequence_num| if a subsequent wakeup is required. Must be
+  // called from the main thread.
+  bool WakeUpForDelayedWork(LazyNow* lazy_now,
+                            base::TimeTicks* out_next_wake_up_time,

[altimin, 2017/03/01 11:23:17]

Nit: time ticks and sequence number seem related. Can we group them in a struct
of sorts and return this new struct directly? It should make code more readable.

[Sami, 2017/03/01 12:17:42]

The other option I considered was to just return a pointer to the PendingTask,
but that seems like it's exposing too much information. Added a struct instead,
WDYT?

+                            int* out_next_wake_up_sequence_num);
 
   base::TimeTicks scheduled_time_domain_wakeup() const {
     return main_thread_only().scheduled_time_domain_wakeup;
   }
 
   void set_scheduled_time_domain_wakeup(
       base::TimeTicks scheduled_time_domain_wakeup) {
     main_thread_only().scheduled_time_domain_wakeup =
         scheduled_time_domain_wakeup;
   }
@@ skipping 156 matching lines @@
   const bool should_report_when_execution_blocked_;
 
   DISALLOW_COPY_AND_ASSIGN(TaskQueueImpl);
 };
 
 }  // namespace internal
 }  // namespace scheduler
 }  // namespace blink
 
 #endif  // THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_TASK_QUEUE_IMPL_H_