Try a different way of unregistering TaskQueues from ThrottlingHelper

components/scheduler/renderer/renderer_scheduler_impl.cc

 // Copyright 2014 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/renderer_scheduler_impl.h"
 
 #include "base/bind.h"
 #include "base/debug/stack_trace.h"
 #include "base/logging.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 206 matching lines @@
   return timer_task_queue;
 }
 
 scoped_ptr<RenderWidgetSchedulingState>
 RendererSchedulerImpl::NewRenderWidgetSchedulingState() {
   return render_widget_scheduler_signals_.NewRenderWidgetSchedulingState();
 }
 
 void RendererSchedulerImpl::OnUnregisterTaskQueue(
     const scoped_refptr<TaskQueue>& task_queue) {
+  if (throttling_helper_.get())
+    throttling_helper_->UnregisterTaskQueue(task_queue.get());
+
   if (loading_task_runners_.find(task_queue) != loading_task_runners_.end()) {
     task_queue->RemoveTaskObserver(
         &MainThreadOnly().loading_task_cost_estimator);
     loading_task_runners_.erase(task_queue);
   } else if (timer_task_runners_.find(task_queue) !=
              timer_task_runners_.end()) {
     task_queue->RemoveTaskObserver(&MainThreadOnly().timer_task_cost_estimator);
     timer_task_runners_.erase(task_queue);
   }
 }
@@ skipping 955 matching lines @@
     }
     MainThreadOnly().have_reported_blocking_intervention_since_navigation =
         true;
     BroadcastConsoleWarning(
         "Deferred long-running timer task(s) to improve scrolling smoothness. "
         "See crbug.com/574343.");
   }
 }
 
 }  // namespace scheduler