[scheduler] Add WakeupBudgetPool.

third_party/WebKit/Source/platform/scheduler/renderer/throttled_time_domain.h

 // Copyright 2016 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_RENDERER_THROTTLED_TIME_DOMAIN_H_
 #define THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_RENDERER_THROTTLED_TIME_DOMAIN_H_
 
 #include "base/macros.h"
 #include "platform/scheduler/base/real_time_domain.h"
 
 namespace blink {
 namespace scheduler {
 
 // A time domain for throttled tasks. behaves like an RealTimeDomain except it
 // relies on the owner (TaskQueueThrottler) to schedule wake-ups.
 class BLINK_PLATFORM_EXPORT ThrottledTimeDomain : public RealTimeDomain {
  public:
   ThrottledTimeDomain(const char* tracing_category);
   ~ThrottledTimeDomain() override;
 
+  void SetNextTaskRunTime(base::TimeTicks run_time);
+
   // TimeDomain implementation:
   const char* GetName() const override;
   void RequestWakeUpAt(base::TimeTicks now, base::TimeTicks run_time) override;
   void CancelWakeUpAt(base::TimeTicks run_time) override;
   base::Optional<base::TimeDelta> DelayTillNextTask(LazyNow* lazy_now) override;
 
   using TimeDomain::WakeUpReadyDelayedQueues;
 
  private:
+  // Next task run time provided by task queue throttler. Note that it does not
+  // get reset, so it is valid only when in the future.
+  base::Optional<base::TimeTicks> next_task_;
+
   DISALLOW_COPY_AND_ASSIGN(ThrottledTimeDomain);
 };
 
 }  // namespace scheduler
 }  // namespace blink
 
 #endif  // THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_RENDERER_THROTTLED_TIME_DOMAIN_H_