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

third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc

Index: third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
diff --git a/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc b/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
index 130d539b4ef053726821e1968e10753b6c00ba7e..9b27402ed8a279e8503bf3d01246f439f58f7c1f 100644
--- a/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
+++ b/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
@@ -247,11 +247,16 @@ void RendererSchedulerImpl::Shutdown() {
   MainThreadOnly().background_main_thread_load_tracker.RecordIdle(now);
   MainThreadOnly().foreground_main_thread_load_tracker.RecordIdle(now);
 
-  task_queue_throttler_.reset();
   helper_.Shutdown();
   idle_helper_.Shutdown();
   MainThreadOnly().was_shutdown = true;
   MainThreadOnly().rail_mode_observer = nullptr;
+
+  // Note this must be done after shutting down |helper_| because otherwise
+  // there's a window where another thread posting a task to a throttled queue
+  // during shutdown might try to access the deleted TimeDomain owned by
+  // |task_queue_throttler_|.
+  task_queue_throttler_.reset();
 }
 
 std::unique_ptr<blink::WebThread> RendererSchedulerImpl::CreateMainThread() {