Move throttling of background timers into the renderer scheduler

components/scheduler/base/time_domain.cc

Index: components/scheduler/base/time_domain.cc
diff --git a/components/scheduler/base/time_domain.cc b/components/scheduler/base/time_domain.cc
index 2abfb522ce86f0d788285b03eb3127d4f1f56de9..40a330a56d5f70056a305de1d244c742dca69eae 100644
--- a/components/scheduler/base/time_domain.cc
+++ b/components/scheduler/base/time_domain.cc
@@ -12,7 +12,7 @@
 
 namespace scheduler {
 
-TimeDomain::TimeDomain() {}
+TimeDomain::TimeDomain() : observer_(nullptr) {}
 
 TimeDomain::~TimeDomain() {}
 
@@ -72,13 +72,19 @@ void TimeDomain::ScheduleDelayedWork(internal::TaskQueueImpl* queue,
     base::TimeDelta delay =
         std::max(base::TimeDelta(), delayed_run_time - lazy_now->Now());
     RequestWakeup(lazy_now, delay);
+    if (observer_)
+      observer_->OnRequestWakeup();
   }
   delayed_wakeup_multimap_.insert(std::make_pair(delayed_run_time, queue));
 }
 
 void TimeDomain::RegisterAsUpdatableTaskQueue(internal::TaskQueueImpl* queue) {
-  base::AutoLock lock(newly_updatable_lock_);
-  newly_updatable_.push_back(queue);
+  {
+    base::AutoLock lock(newly_updatable_lock_);
+    newly_updatable_.push_back(queue);
+  }
+  if (observer_)
+    observer_->OnRegisterAsUpdatableTaskQueue();
 }
 
 void TimeDomain::UnregisterAsUpdatableTaskQueue(
@@ -148,6 +154,10 @@ void TimeDomain::WakeupReadyDelayedQueues(LazyNow* lazy_now) {
   }
 }
 
+void TimeDomain::SetObserver(Observer* observer) {

[Sami, 2015/11/24 12:48:48]

Can we require this to be passed in at construction time and to outlive the time
domain? Otherwise this needs a lock :\

Guaranteeing the lifetime will be tricky with TimeDomain being refcounted,
though. I wonder if that can be changed?

[alex clarke (OOO till 29th), 2015/11/25 12:29:36]

Agreed this is a bit subtle thanks to the ownership.

I think we are OK with this being passed in via the constructor.

+  observer_ = observer;
+}
+
 bool TimeDomain::NextScheduledRunTime(base::TimeTicks* out_time) const {
   if (delayed_wakeup_multimap_.empty())
     return false;