[scheduler] Change TaskQueue observer call mechanism.

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

Index: third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h
diff --git a/third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h b/third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h
index 3de8f3bc34b8ba610005798116ccb4758e9de41e..454a05956838ce4a9caea0dd309f1dbb82b3617e 100644
--- a/third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h
+++ b/third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h
@@ -142,7 +142,7 @@ class PLATFORM_EXPORT TaskQueueImpl final : public TaskQueue {
   bool IsQueueEnabled() const override;
   bool IsEmpty() const override;
   size_t GetNumberOfPendingTasks() const override;
-  bool HasPendingImmediateWork() const override;
+  bool HasTaskToRunImmediately() const override;
   base::Optional<base::TimeTicks> GetNextScheduledWakeUp() override;
   void SetQueuePriority(QueuePriority priority) override;
   QueuePriority GetQueuePriority() const override;
@@ -177,6 +177,14 @@ class PLATFORM_EXPORT TaskQueueImpl final : public TaskQueue {
   void NotifyWillProcessTask(const base::PendingTask& pending_task);
   void NotifyDidProcessTask(const base::PendingTask& pending_task);
 
+  void SetScheduledTimeDomainWakeUp(

[alex clarke (OOO till 29th), 2017/05/09 12:50:50]

Can you please add a brief comment mentioning that there is exactly one wake up,
calling this cancels any previous wake up and if |scheduled_time_domain_wake_up|
is nullopt then no wakeup will occur. 

[altimin, 2017/05/09 13:15:04]

Done.

+      base::Optional<base::TimeTicks> scheduled_time_domain_wake_up);

[alex clarke (OOO till 29th), 2017/05/09 12:50:50]

Also please document which threads these two calls can be called from.

[altimin, 2017/05/09 13:15:04]

Done.

+
+  // Check for pending immediate work, but do not look in

[alex clarke (OOO till 29th), 2017/05/09 11:51:28]

s/but do not look in/but does not look in

Also please reformat.

[altimin, 2017/05/09 13:15:04]

Done.

+  // delayed_incoming_queue.
+  // Used to check if we need to generate notifications about delayed work.
+  bool HasPendingImmediateWork();
+
   WorkQueue* delayed_work_queue() {
     return main_thread_only().delayed_work_queue.get();
   }
@@ -202,16 +210,10 @@ class PLATFORM_EXPORT TaskQueueImpl final : public TaskQueue {
   // any. Must be called from the main thread.
   base::Optional<DelayedWakeUp> WakeUpForDelayedWork(LazyNow* lazy_now);
 
-  base::TimeTicks scheduled_time_domain_wake_up() const {
+  base::Optional<base::TimeTicks> scheduled_time_domain_wake_up() const {

[alex clarke (OOO till 29th), 2017/05/09 11:51:28]

Why do we need to use optional here?  What's wrong with using zero as no wakeup?

[altimin, 2017/05/09 13:15:04]

I prefer explicit base::nullopt to describe "no wake-up" situation. Helps with
readability.

     return main_thread_only().scheduled_time_domain_wake_up;
   }
 
-  void set_scheduled_time_domain_wake_up(
-      base::TimeTicks scheduled_time_domain_wake_up) {
-    main_thread_only().scheduled_time_domain_wake_up =
-        scheduled_time_domain_wake_up;
-  }
-
   HeapHandle heap_handle() const { return main_thread_only().heap_handle; }
 
   void set_heap_handle(HeapHandle heap_handle) {
@@ -285,7 +287,7 @@ class PLATFORM_EXPORT TaskQueueImpl final : public TaskQueue {
     int voter_refcount;
     base::trace_event::BlameContext* blame_context;  // Not owned.
     EnqueueOrder current_fence;
-    base::TimeTicks scheduled_time_domain_wake_up;
+    base::Optional<base::TimeTicks> scheduled_time_domain_wake_up;
   };
 
   ~TaskQueueImpl() override;
@@ -347,8 +349,6 @@ class PLATFORM_EXPORT TaskQueueImpl final : public TaskQueue {
   // Schedules delayed work on time domain and calls the observer.
   void ScheduleDelayedWorkInTimeDomain(base::TimeTicks now);
 
-  void NotifyWakeUpChangedOnMainThread(base::TimeTicks wake_up);
-
   const base::PlatformThreadId thread_id_;
 
   mutable base::Lock any_thread_lock_;