Move throttling of background timers into the renderer scheduler

components/scheduler/base/virtual_time_domain.cc

Index: components/scheduler/base/virtual_time_domain.cc
diff --git a/components/scheduler/base/virtual_time_domain.cc b/components/scheduler/base/virtual_time_domain.cc
index 32510394fda1f744ccc79657b91210757fecb1e4..0ed6abbc2c3b99abc90c56a7b57da60ef450b6a2 100644
--- a/components/scheduler/base/virtual_time_domain.cc
+++ b/components/scheduler/base/virtual_time_domain.cc
@@ -10,8 +10,9 @@
 
 namespace scheduler {
 
-VirtualTimeDomain::VirtualTimeDomain(base::TimeTicks initial_time)
-    : now_(initial_time) {}
+VirtualTimeDomain::VirtualTimeDomain(TimeDomain::Observer* observer,
+                                     base::TimeTicks initial_time)
+    : TimeDomain(observer), now_(initial_time) {}
 
 VirtualTimeDomain::~VirtualTimeDomain() {}
 
@@ -44,6 +45,8 @@ 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_);
 }