Try a different way of unregistering TaskQueues from ThrottlingHelper

components/scheduler/renderer/throttling_helper.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/renderer/throttling_helper.h"
 
 #include "base/logging.h"
 #include "components/scheduler/base/real_time_domain.h"
 #include "components/scheduler/base/virtual_time_domain.h"
 #include "components/scheduler/child/scheduler_tqm_delegate.h"
@@ skipping 61 matching lines @@
 
   if (iter != throttled_queues_.end() && --iter->second == 0) {
     // The refcount has become zero, we need to unthrottle the queue.
     throttled_queues_.erase(iter);
 
     task_queue->SetTimeDomain(renderer_scheduler_->real_time_domain());
     task_queue->SetPumpPolicy(TaskQueue::PumpPolicy::AUTO);
   }
 }
 
+void ThrottlingHelper::UnregisterTaskQueue(TaskQueue* task_queue) {
+  throttled_queues_.erase(task_queue);
+}
+
 void ThrottlingHelper::OnTimeDomainHasImmediateWork() {
   // Forward to the main thread if called from another thread.
   if (!task_runner_->RunsTasksOnCurrentThread()) {
     task_runner_->PostTask(FROM_HERE, forward_immediate_work_closure_);
     return;
   }
   TRACE_EVENT0(tracing_category_,
                "ThrottlingHelper::OnTimeDomainHasImmediateWork");
   base::TimeTicks now = tick_clock_->NowTicks();
   MaybeSchedulePumpThrottledTasksLocked(FROM_HERE, now, now);
@@ skipping 60 matching lines @@
 
   pending_pump_throttled_tasks_runtime_ = throttled_runtime;
 
   suspend_timers_when_backgrounded_closure_.Cancel();
   task_runner_->PostDelayedTask(
       from_here, suspend_timers_when_backgrounded_closure_.callback(),
       pending_pump_throttled_tasks_runtime_ - now);
 }
 
 }  // namespace scheduler