Try a different way of unregistering TaskQueues from ThrottlingHelper

components/scheduler/renderer/throttling_helper.h

 // 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.
 
 #ifndef COMPONENTS_SCHEDULER_RENDERER_THROTTLING_HELPER_H_
 #define COMPONENTS_SCHEDULER_RENDERER_THROTTLING_HELPER_H_
 
 #include <set>
 
 #include "base/macros.h"
@@ skipping 21 matching lines @@
 
   // Increments the throttled refcount and causes |task_queue| to be throttled
   // if its not already throttled.
   void IncreaseThrottleRefCount(TaskQueue* task_queue);
 
   // If the refcouint is non-zero it's decremented.  If the throttled refcount
   // becomes zero then |task_queue| is unthrottled.  If the refcount was already
   // zero this function does nothing.
   void DecreaseThrottleRefCount(TaskQueue* task_queue);
 
+  // Removes |task_queue| from |throttled_queues_|.
+  void UnregisterTaskQueue(TaskQueue* task_queue);
+
   const VirtualTimeDomain* time_domain() const { return time_domain_.get(); }
 
   static base::TimeTicks ThrottledRunTime(base::TimeTicks unthrottled_runtime);
 
   const scoped_refptr<TaskQueue>& task_runner() const { return task_runner_; }
 
  private:
   using TaskQueueMap = std::map<TaskQueue*, size_t>;
 
   void PumpThrottledTasks();
@@ skipping 18 matching lines @@
   base::TimeTicks pending_pump_throttled_tasks_runtime_;
 
   base::WeakPtrFactory<ThrottlingHelper> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ThrottlingHelper);
 };
 
 }  // namespace scheduler
 
 #endif  // COMPONENTS_SCHEDULER_RENDERER_THROTTLING_HELPER_H_