Reduce the number of delayed tasks on chromium run loop

components/scheduler/base/real_time_domain.cc

Index: components/scheduler/base/real_time_domain.cc
diff --git a/components/scheduler/base/real_time_domain.cc b/components/scheduler/base/real_time_domain.cc
index 8a57a0415cf3181d1d2117a587b3c7009459417e..4d3bfc7d30043eee8e678740e16e694e3e24f4de 100644
--- a/components/scheduler/base/real_time_domain.cc
+++ b/components/scheduler/base/real_time_domain.cc
@@ -10,29 +10,58 @@
 
 namespace scheduler {
 
-RealTimeDomain::RealTimeDomain(
+RealTimeDomain::RealTimeDomain() {}
+
+RealTimeDomain::~RealTimeDomain() {}
+
+void RealTimeDomain::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) {
+    base::Closure do_work_closure) {
+  task_queue_manager_delegate_ = task_queue_manager_delegate;
+  do_work_closure_ = do_work_closure;
   DCHECK(task_queue_manager_delegate_);
 }
 
-RealTimeDomain::~RealTimeDomain() {}
-
 LazyNow RealTimeDomain::CreateLazyNow() {
+  DCHECK(task_queue_manager_delegate_);
   return LazyNow(task_queue_manager_delegate_);
 }
 
-void RealTimeDomain::RequestWakeup(base::TimeDelta delay) {
-  task_queue_manager_delegate_->PostDelayedTask(FROM_HERE, do_work_closure_,
-                                                delay);
+void RealTimeDomain::RequestWakeup(LazyNow* lazy_now, base::TimeDelta delay) {
+  PostWrappedDoWork(lazy_now->Now(), lazy_now->Now() + delay);
 }
 
 bool RealTimeDomain::MaybeAdvanceTime() {
+  base::TimeTicks next_run_time;
+  if (!NextScheduledRunTime(&next_run_time))
+    return false;
+
+  DCHECK(task_queue_manager_delegate_);
+  base::TimeTicks now = task_queue_manager_delegate_->NowTicks();
+  if (now >= next_run_time)
+    return true;
+
+  PostWrappedDoWork(now, next_run_time);
   return false;
 }
 
+void RealTimeDomain::PostWrappedDoWork(base::TimeTicks now,
+                                       base::TimeTicks run_time) {
+  DCHECK_GE(run_time, now);
+  DCHECK(task_queue_manager_delegate_);
+  if (pending_wakeups_.insert(run_time).second) {
+    task_queue_manager_delegate_->PostDelayedTask(
+        FROM_HERE,
+        base::Bind(&RealTimeDomain::WrappedDoWorkTask, this, run_time),

[Sami, 2015/11/20 19:20:00]

I think this might need to be a weak pointer to guard against the domain getting
destroyed before the timeout expires.

[alex clarke (OOO till 29th), 2015/11/23 10:11:51]

Done.

+        run_time - now);
+  }
+}
+
+void RealTimeDomain::WrappedDoWorkTask(base::TimeTicks run_time) {
+  pending_wakeups_.erase(run_time);
+  do_work_closure_.Run();
+}
+
 void RealTimeDomain::AsValueIntoInternal(
     base::trace_event::TracedValue* state) const {}