Revert of Move throttling of background timers into the renderer scheduler

components/scheduler/base/virtual_time_domain.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 "components/scheduler/base/virtual_time_domain.h"
 
 #include "base/bind.h"
 #include "components/scheduler/base/task_queue_impl.h"
 #include "components/scheduler/base/task_queue_manager_delegate.h"
 
 namespace scheduler {
 
-VirtualTimeDomain::VirtualTimeDomain(TimeDomain::Observer* observer,
-                                     base::TimeTicks initial_time)
-    : TimeDomain(observer), now_(initial_time) {}
+VirtualTimeDomain::VirtualTimeDomain(base::TimeTicks initial_time)
+    : now_(initial_time) {}
 
 VirtualTimeDomain::~VirtualTimeDomain() {}
 
 void VirtualTimeDomain::OnRegisterWithTaskQueueManager(
     TaskQueueManagerDelegate* task_queue_manager_delegate,
     base::Closure do_work_closure) {
   task_queue_manager_delegate_ = task_queue_manager_delegate;
   do_work_closure_ = do_work_closure;
   DCHECK(task_queue_manager_delegate_);
 }
@@ skipping 12 matching lines @@
   return false;
 }
 
 void VirtualTimeDomain::AsValueIntoInternal(
     base::trace_event::TracedValue* state) const {}
 
 void VirtualTimeDomain::AdvanceTo(base::TimeTicks now) {
   base::AutoLock lock(lock_);
   DCHECK_GE(now, now_);
   now_ = now;
-  DCHECK(task_queue_manager_delegate_);
-
   task_queue_manager_delegate_->PostTask(FROM_HERE, do_work_closure_);
 }
 
 const char* VirtualTimeDomain::GetName() const {
   return "VirtualTimeDomain";
 }
 
 }  // namespace scheduler