Reduce the number of delayed tasks on chromium run loop

components/scheduler/base/real_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/real_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 {
 
-RealTimeDomain::RealTimeDomain(
+RealTimeDomain::RealTimeDomain() : weak_factory_(this) {}
+
+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,
+                   weak_factory_.GetWeakPtr(), run_time),
+        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 {}
 
 const char* RealTimeDomain::GetName() const {
   return "RealTimeDomain";
 }
 
 }  // namespace scheduler