Revert of Move throttling of background timers into the renderer scheduler

components/scheduler/base/virtual_time_domain.h

 // 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.
 
 #ifndef COMPONENTS_SCHEDULER_BASE_VIRTUAL_TIME_DOMAIN_H_
 #define COMPONENTS_SCHEDULER_BASE_VIRTUAL_TIME_DOMAIN_H_
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "components/scheduler/base/time_domain.h"
 #include "components/scheduler/scheduler_export.h"
 
 namespace scheduler {
 class TaskQueueManagerDelegate;
 
 class SCHEDULER_EXPORT VirtualTimeDomain : public TimeDomain {
  public:
-  VirtualTimeDomain(TimeDomain::Observer* observer,
-                    base::TimeTicks initial_time);
-  ~VirtualTimeDomain() override;
+  VirtualTimeDomain(base::TimeTicks initial_time);
 
   // TimeDomain implementation:
   LazyNow CreateLazyNow() override;
   bool MaybeAdvanceTime() override;
   const char* GetName() const override;
 
   // Advances this time domain to |now|. NOTE |now| is supposed to be
   // monotonically increasing.
   void AdvanceTo(base::TimeTicks now);
 
  protected:
   void OnRegisterWithTaskQueueManager(
       TaskQueueManagerDelegate* task_queue_manager_delegate,
       base::Closure do_work_closure) override;
   void RequestWakeup(LazyNow* lazy_now, base::TimeDelta delay) override;
   void AsValueIntoInternal(
       base::trace_event::TracedValue* state) const override;
 
  private:
   mutable base::Lock lock_;  // Protects |now_|.
   base::TimeTicks now_;
 
   TaskQueueManagerDelegate* task_queue_manager_delegate_;  // NOT OWNED
   base::Closure do_work_closure_;
 
+  ~VirtualTimeDomain() override;
+
   DISALLOW_COPY_AND_ASSIGN(VirtualTimeDomain);
 };
 
 }  // namespace scheduler
 
 #endif  // COMPONENTS_SCHEDULER_BASE_VIRTUAL_TIME_DOMAIN_H_