[scheduler] Implement time-based cpu throttling.

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

 // 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.
 
 #include "platform/scheduler/base/task_queue_impl.h"
 
 #include "base/trace_event/blame_context.h"
 #include "platform/scheduler/base/task_queue_manager.h"
 #include "platform/scheduler/base/task_queue_manager_delegate.h"
 #include "platform/scheduler/base/time_domain.h"
@@ skipping 515 matching lines @@
       main_thread_only().delayed_incoming_queue.begin()->delayed_run_time <=
           main_thread_only().time_domain->CreateLazyNow().Now()) {
     return true;
   }
 
   // Finally tasks on |immediate_incoming_queue| count as immediate work.
   base::AutoLock lock(any_thread_lock_);
   return !any_thread().immediate_incoming_queue.empty();
 }
 
+bool TaskQueueImpl::NextScheduledWakeUp(base::TimeTicks* wakeup) {
+  LazyNow lazy_now = main_thread_only().time_domain->CreateLazyNow();
+  MoveReadyDelayedTasksToDelayedWorkQueue(&lazy_now);
+
+  if (main_thread_only().delayed_incoming_queue.empty())
+    return false;
+
+  if (wakeup) {

[alex clarke (OOO till 29th), 2016/09/07 15:13:07]

I don't think we should allow |wakeup| to be null.  BTW
main_thread_only().delayed_incoming_queue.begin() is O(1).

[altimin, 2016/09/09 15:43:57]

Done.

+    *wakeup =
+        main_thread_only().delayed_incoming_queue.begin()->delayed_run_time;
+  }
+  return true;
+}
+
 void TaskQueueImpl::MoveReadyDelayedTasksToDelayedWorkQueue(LazyNow* lazy_now) {
   // Enqueue all delayed tasks that should be running now.
   while (!main_thread_only().delayed_incoming_queue.empty()) {
     DelayedRunTimeQueue::iterator next_task =
         main_thread_only().delayed_incoming_queue.begin();
     if (next_task->delayed_run_time > lazy_now->Now())
       break;
     // TODO(alexclarke): Use extract() when C++17 is allowed.
     Task& task = const_cast<Task&>(*next_task);
     task.set_enqueue_order(
@@ skipping 311 matching lines @@
   state->SetBoolean("is_high_res", task.is_high_res);
   state->SetDouble(
       "delayed_run_time",
       (task.delayed_run_time - base::TimeTicks()).InMicroseconds() / 1000.0L);
   state->EndDictionary();
 }
 
 }  // namespace internal
 }  // namespace scheduler
 }  // namespace blink