[Try # 3] Scheduler refactoring to virtually eliminate redundant DoWorks

third_party/WebKit/Source/platform/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 "platform/scheduler/base/real_time_domain.h"
 
 #include "base/bind.h"
 #include "platform/scheduler/base/task_queue_impl.h"
 #include "platform/scheduler/base/task_queue_manager.h"
 #include "platform/scheduler/base/task_queue_manager_delegate.h"
@@ skipping 28 matching lines @@
   return task_queue_manager_->delegate()->NowTicks();
 }
 
 void RealTimeDomain::RequestWakeup(base::TimeTicks now, base::TimeDelta delay) {
   // NOTE this is only called if the scheduled runtime is sooner than any
   // previously scheduled runtime, or there is no (outstanding) previously
   // scheduled runtime.
   task_queue_manager_->MaybeScheduleDelayedWork(FROM_HERE, now, delay);
 }
 
-bool RealTimeDomain::MaybeAdvanceTime() {
+base::Optional<base::TimeDelta> RealTimeDomain::DelayTillNextTask(
+    LazyNow* lazy_now) {
   base::TimeTicks next_run_time;
   if (!NextScheduledRunTime(&next_run_time))
-    return false;
+    return base::Optional<base::TimeDelta>();
 
-  base::TimeTicks now = Now();
+  base::TimeTicks now = lazy_now->Now();
   if (now >= next_run_time)
-    return true;  // Causes DoWork to post a continuation.
+    return base::TimeDelta();  // Makes DoWork post an immediate continuation.
 
   base::TimeDelta delay = next_run_time - now;
-  TRACE_EVENT1(tracing_category_, "RealTimeDomain::MaybeAdvanceTime",
+  TRACE_EVENT1(tracing_category_, "RealTimeDomain::DelayTillNextTask",
                "delay_ms", delay.InMillisecondsF());
 
-  // The next task is sometime in the future, make sure we schedule a DoWork to
-  // run it.
-  task_queue_manager_->MaybeScheduleDelayedWork(FROM_HERE, now, delay);
-  return false;
+  // The next task is sometime in the future. DoWork will make sure it gets
+  // run at the right time..
+  return delay;
 }
 
 void RealTimeDomain::AsValueIntoInternal(
     base::trace_event::TracedValue* state) const {}
 
 const char* RealTimeDomain::GetName() const {
   return "RealTimeDomain";
 }
 }  // namespace scheduler
 }  // namespace blink