Revert of Move throttling of background timers into the renderer scheduler

components/scheduler/base/virtual_time_domain.h

Index: components/scheduler/base/virtual_time_domain.h
diff --git a/components/scheduler/base/virtual_time_domain.h b/components/scheduler/base/virtual_time_domain.h
index 78239c1c26dc780234c1b93a55db4bc65a6c2409..ce1f99aac1b1896b5861718ff39ccb3697008c37 100644
--- a/components/scheduler/base/virtual_time_domain.h
+++ b/components/scheduler/base/virtual_time_domain.h
@@ -15,9 +15,7 @@
 
 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;
@@ -43,6 +41,8 @@
   TaskQueueManagerDelegate* task_queue_manager_delegate_;  // NOT OWNED
   base::Closure do_work_closure_;
 
+  ~VirtualTimeDomain() override;
+
   DISALLOW_COPY_AND_ASSIGN(VirtualTimeDomain);
 };