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

third_party/WebKit/Source/platform/scheduler/renderer/task_queue_throttler.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/renderer/task_queue_throttler.h"
 
 #include <cstdint>
 
 #include "base/format_macros.h"
 #include "base/logging.h"
@@ skipping 282 matching lines @@
   pump_throttled_tasks_closure_.Reset(base::Bind(
       &TaskQueueThrottler::PumpThrottledTasks, weak_factory_.GetWeakPtr()));
   forward_immediate_work_callback_ =
       base::Bind(&TaskQueueThrottler::OnTimeDomainHasImmediateWork,
                  weak_factory_.GetWeakPtr());
 
   renderer_scheduler_->RegisterTimeDomain(time_domain_.get());
 }
 
 TaskQueueThrottler::~TaskQueueThrottler() {
+  // If the shutdown has been called we can just bail out.
+  if (!renderer_scheduler_->real_time_domain())
+    return;
   // It's possible for queues to be still throttled, so we need to tidy up
   // before unregistering the time domain.
   for (const TaskQueueMap::value_type& map_entry : queue_details_) {
     TaskQueue* task_queue = map_entry.first;
     if (IsThrottled(task_queue)) {
       task_queue->SetTimeDomain(renderer_scheduler_->real_time_domain());
       task_queue->RemoveFence();
     }
   }
 
@@ skipping 326 matching lines @@
     queue->SetTimeDomain(time_domain_.get());
     MaybeSchedulePumpQueue(FROM_HERE, lazy_now.Now(), queue,
                            GetNextAllowedRunTime(lazy_now.Now(), queue));
   }
 
   TRACE_EVENT0(tracing_category_, "TaskQueueThrottler_EnableThrottling");
 }
 
 }  // namespace scheduler
 }  // namespace blink