Add a sanity DCHECK to TimeDomain::ScheduleDelayedWork

This patch removes TimeNomain::MigrateQueue since it's now superfluous.

Was part of https://codereview.chromium.org/2546423002/

BUG=578176

Review-Url: https://codereview.chromium.org/2651003002
Cr-Commit-Position: refs/heads/master@{#446123}

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

@@ -576,10 +576,16 @@ void TaskQueueImpl::SetTimeDomain(TimeDomain* time_domain) {
 
     any_thread().time_domain = time_domain;
   }
-  // We rely here on TimeDomain::MigrateQueue being thread-safe to use with
-  // TimeDomain::Register.
-  main_thread_only().time_domain->MigrateQueue(this, time_domain);
+
+  main_thread_only().time_domain->UnregisterQueue(this);
   main_thread_only().time_domain = time_domain;
+  time_domain->RegisterQueue(this);
+
+  if (!main_thread_only().delayed_incoming_queue.empty()) {
+    time_domain->ScheduleDelayedWork(
+        this, main_thread_only().delayed_incoming_queue.top().delayed_run_time,
+        time_domain->Now());
+  }
 }
 
 TimeDomain* TaskQueueImpl::GetTimeDomain() const {

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

@@ -31,31 +31,11 @@ void TimeDomain::UnregisterQueue(internal::TaskQueueImpl* queue) {
   CancelDelayedWork(queue);
 }
 
-void TimeDomain::MigrateQueue(internal::TaskQueueImpl* queue,
-                              TimeDomain* destination_time_domain) {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  DCHECK_EQ(queue->GetTimeDomain(), this);
-  DCHECK(destination_time_domain);
-
-  // If no wakeup has been requested then bail out.
-  if (!queue->heap_handle().IsValid())
-    return;
-
-  base::TimeTicks wake_up_time = queue->scheduled_time_domain_wakeup();
-  DCHECK_NE(wake_up_time, base::TimeTicks());
-
-  // O(log n)
-  delayed_wakeup_queue_.erase(queue->heap_handle());
-
-  base::TimeTicks destination_now = destination_time_domain->Now();
-  destination_time_domain->ScheduleDelayedWork(queue, wake_up_time,
-                                               destination_now);
-}
-
 void TimeDomain::ScheduleDelayedWork(internal::TaskQueueImpl* queue,
                                      base::TimeTicks delayed_run_time,
                                      base::TimeTicks now) {
   DCHECK(main_thread_checker_.CalledOnValidThread());
+  DCHECK_EQ(queue->GetTimeDomain(), this);
   // We only want to store a single wakeup per queue, so we need to remove any
   // previously registered wake up for |queue|.
   if (queue->heap_handle().IsValid()) {

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

@@ -82,11 +82,6 @@ class BLINK_PLATFORM_EXPORT TimeDomain {
 
   void AsValueInto(base::trace_event::TracedValue* state) const;
 
-  // Migrates |queue| from this time domain to |destination_time_domain|.
-  // Main-thread only.
-  void MigrateQueue(internal::TaskQueueImpl* queue,
-                    TimeDomain* destination_time_domain);
-
   // If there is a scheduled delayed task, |out_task_queue| is set to the queue
   // the next task was posted to and it returns true.  Returns false otherwise.
   bool NextScheduledTaskQueue(TaskQueue** out_task_queue) const;