Don't use PostTask queueing between compositor and main thread.

content/renderer/input/input_event_filter.h

 // Copyright 2013 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_INPUT_EVENT_FILTER_H_
 #define CONTENT_RENDERER_INPUT_INPUT_EVENT_FILTER_H_
 
 #include <queue>
 #include <set>
 #include <unordered_map>
@@ skipping 60 matching lines @@
                                blink::WebInputEvent::Type type,
                                InputEventAckState ack_result) override;
 
   // IPC::MessageFilter methods:
   void OnFilterAdded(IPC::Sender* sender) override;
   void OnFilterRemoved() override;
   void OnChannelClosing() override;
   bool OnMessageReceived(const IPC::Message& message) override;
 
   // MainThreadEventQueueClient methods:
-  void SendEventToMainThread(int routing_id,
-                             const blink::WebInputEvent* event,
-                             const ui::LatencyInfo& latency,
-                             InputEventDispatchType dispatch_type) override;
+  void HandleEventOnMainThread(int routing_id,
+                               const blink::WebInputEvent* event,
+                               const ui::LatencyInfo& latency,
+                               InputEventDispatchType dispatch_type) override;
   // Send an InputEventAck IPC message. |touch_event_id| represents
   // the unique event id for the original WebTouchEvent and should
   // be 0 if otherwise. See WebInputEventTraits::GetUniqueTouchEventId.
   void SendInputEventAck(int routing_id,
                          blink::WebInputEvent::Type type,
                          InputEventAckState ack_result,
                          uint32_t touch_event_id) override;
 
  private:
   ~InputEventFilter() override;
@@ skipping 14 matching lines @@
   scoped_refptr<base::SingleThreadTaskRunner> target_task_runner_;
   Handler handler_;
 
   // Protects access to routes_.
   base::Lock routes_lock_;
 
   // Indicates the routing_ids for which input events should be filtered.
   std::set<int> routes_;
 
   using RouteQueueMap =
-      std::unordered_map<int, std::unique_ptr<MainThreadEventQueue>>;
+      std::unordered_map<int, scoped_refptr<MainThreadEventQueue>>;
   RouteQueueMap route_queues_;
 
   // Used to intercept overscroll notifications while an event is being
   // dispatched.  If the event causes overscroll, the overscroll metadata can be
   // bundled in the event ack, saving an IPC.  Note that we must continue
   // supporting overscroll IPC notifications due to fling animation updates.
   std::unique_ptr<DidOverscrollParams>* current_overscroll_params_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_INPUT_INPUT_EVENT_FILTER_H_