[scheduler] Change TaskQueue observer call mechanism.

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

Index: third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.cc
diff --git a/third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.cc b/third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.cc
index 6333a681ebb1329cbce7225c37c9b2325e2d1d28..75b161a27b060b143d9cb36ddc4adf8e60c78692 100644
--- a/third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.cc
+++ b/third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.cc
@@ -402,7 +402,7 @@ size_t TaskQueueImpl::GetNumberOfPendingTasks() const {
   return task_count;
 }
 
-bool TaskQueueImpl::HasPendingImmediateWork() const {
+bool TaskQueueImpl::HasTaskToRunImmediately() const {
   // Any work queue tasks count as immediate work.
   if (!main_thread_only().delayed_work_queue->Empty() ||
       !main_thread_only().immediate_work_queue->Empty()) {
@@ -821,8 +821,11 @@ void TaskQueueImpl::EnableOrDisableWithSelector(bool enable) {
     return;
 
   if (enable) {
-    if (HasPendingImmediateWork())
-      NotifyWakeUpChangedOnMainThread(base::TimeTicks());
+    if (HasPendingImmediateWork() && main_thread_only().observer) {
+      // Delayed work notification will be issued via time domain.
+      main_thread_only().observer->OnQueueNextWakeUpChanged(this,
+                                                            base::TimeTicks());
+    }
 
     ScheduleDelayedWorkInTimeDomain(main_thread_only().time_domain->Now());
 
@@ -899,14 +902,36 @@ void TaskQueueImpl::ScheduleDelayedWorkInTimeDomain(base::TimeTicks now) {
   main_thread_only().time_domain->ScheduleDelayedWork(
       this, main_thread_only().delayed_incoming_queue.top().delayed_wake_up(),
       now);
+}
+
+void TaskQueueImpl::SetScheduledTimeDomainWakeUp(
+    base::Optional<base::TimeTicks> scheduled_time_domain_wake_up) {
+  main_thread_only().scheduled_time_domain_wake_up =
+      scheduled_time_domain_wake_up;
+
+  if (!scheduled_time_domain_wake_up)

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

nit: Stylistically we tend to collapse all these onto one if

[altimin, 2017/05/09 13:15:03]

I think that in this case the conditions are different and they warrant separate
ifs.

[alex clarke (OOO till 29th), 2017/05/09 19:18:42]

One of the style guide rules is to be consistent with other code. Elsewhere in
the scheduler we tend to merge these into one line.  I don't see anything
special here that warrants them being on multiple lines. I don't think it helps
readability ether.

[altimin, 2017/05/10 10:42:25]

Done.

+    return;
+  if (!main_thread_only().observer)
+    return;
+  // If queue has immediate work an appropriate notification has already
+  // been issued.
+  if (HasPendingImmediateWork())
+    return;
 
-  NotifyWakeUpChangedOnMainThread(

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

For my education, was this a bug since it looks like it would have overwritten
the immediate  time from TaskQueueImpl::EnableOrDisableWithSelector?

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

Yes, but strictly speaking this wasn't a real bug because task queue throttler
is the only user and it is resistant to extra notifications.

-      main_thread_only().delayed_incoming_queue.top().delayed_run_time);
+  main_thread_only().observer->OnQueueNextWakeUpChanged(
+      this, scheduled_time_domain_wake_up.value());
 }
 
-void TaskQueueImpl::NotifyWakeUpChangedOnMainThread(base::TimeTicks wake_up) {
-  if (main_thread_only().observer)
-    main_thread_only().observer->OnQueueNextWakeUpChanged(this, wake_up);
+bool TaskQueueImpl::HasPendingImmediateWork() {
+  // Any work queue tasks count as immediate work.
+  if (!main_thread_only().delayed_work_queue->Empty() ||
+      !main_thread_only().immediate_work_queue->Empty()) {
+    return true;
+  }
+
+  // Finally tasks on |immediate_incoming_queue| count as immediate work.
+  base::AutoLock lock(immediate_incoming_queue_lock_);
+  return !immediate_incoming_queue().empty();
 }
 
 }  // namespace internal