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

third_party/WebKit/Source/platform/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 "platform/scheduler/renderer/renderer_scheduler_impl.h"
 
 #include "base/bind.h"
 #include "base/debug/stack_trace.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 229 matching lines @@
     : last_input_type(blink::WebInputEvent::Undefined),
       main_thread_seems_unresponsive(false) {}
 
 RendererSchedulerImpl::CompositorThreadOnly::~CompositorThreadOnly() {}
 
 void RendererSchedulerImpl::Shutdown() {
   base::TimeTicks now = tick_clock()->NowTicks();
   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() {
   return base::MakeUnique<WebThreadImplForRendererScheduler>(this);
 }
 
 scoped_refptr<TaskQueue> RendererSchedulerImpl::DefaultTaskRunner() {
   return helper_.DefaultTaskRunner();
 }
 
@@ skipping 1609 matching lines @@
     case TimeDomainType::VIRTUAL:
       return "virtual";
     default:
       NOTREACHED();
       return nullptr;
   }
 }
 
 }  // namespace scheduler
 }  // namespace blink