Force events to be non blocking if main thread is unresponsive.

content/renderer/input/main_thread_event_queue.h

 // Copyright 2016 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 CONTENT_RENDERER_INPUT_MAIN_THREAD_EVENT_QUEUE_H_
 #define CONTENT_RENDERER_INPUT_MAIN_THREAD_EVENT_QUEUE_H_
 
 #include <deque>
 #include "base/feature_list.h"
 #include "content/common/content_export.h"
@@ skipping 131 matching lines @@
 
   bool IsRafAlignedInputDisabled();
   bool IsRafAlignedEvent(const std::unique_ptr<EventWithDispatchType>& event);
 
   friend class MainThreadEventQueueTest;
   int routing_id_;
   MainThreadEventQueueClient* client_;
   std::unique_ptr<EventWithDispatchType> in_flight_event_;
   bool last_touch_start_forced_nonblocking_due_to_fling_;
   bool enable_fling_passive_listener_flag_;
+  bool enable_non_blocking_due_to_main_thread_responsiveness_flag_;
   bool handle_raf_aligned_touch_input_;
   bool handle_raf_aligned_mouse_input_;
 
   // Contains data to be shared between main thread and compositor thread.
   struct SharedState {
     SharedState();
     ~SharedState();
 
     WebInputEventQueue<EventWithDispatchType> events_;
     bool sent_main_frame_request_;
   };
 
   // Lock used to serialize |shared_state_|.
   base::Lock shared_state_lock_;
   SharedState shared_state_;
 
   scoped_refptr<base::SingleThreadTaskRunner> main_task_runner_;
   blink::scheduler::RendererScheduler* renderer_scheduler_;
 
   DISALLOW_COPY_AND_ASSIGN(MainThreadEventQueue);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_INPUT_MAIN_THREAD_EVENT_QUEUE_H_