Animated scroll shouldn't consume unhandled scrolls for OOPIFs.

content/browser/renderer_host/input/mouse_wheel_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_BROWSER_RENDERER_HOST_INPUT_MOUSE_WHEEL_EVENT_QUEUE_H_
 #define CONTENT_BROWSER_RENDERER_HOST_INPUT_MOUSE_WHEEL_EVENT_QUEUE_H_
 
 #include <deque>
 #include <memory>
 
@@ skipping 19 matching lines @@
  public:
   virtual ~MouseWheelEventQueueClient() {}
 
   virtual void SendMouseWheelEventImmediately(
       const MouseWheelEventWithLatencyInfo& event) = 0;
   virtual void ForwardGestureEventWithLatencyInfo(
       const blink::WebGestureEvent& event,
       const ui::LatencyInfo& latency_info) = 0;
   virtual void OnMouseWheelEventAck(const MouseWheelEventWithLatencyInfo& event,
                                     InputEventAckState ack_result) = 0;
+  virtual bool is_in_gesture_scroll() = 0;
 };
 
 // A queue for throttling and coalescing mouse wheel events.
 class CONTENT_EXPORT MouseWheelEventQueue {
  public:
   // The |client| must outlive the MouseWheelEventQueue. |send_gestures|
   // indicates whether mouse wheel events should generate
   // Scroll[Begin|Update|End] on unhandled acknowledge events.
   // |scroll_transaction_ms| is the duration in which the
   // ScrollEnd should be sent after a ScrollUpdate.
@@ skipping 33 matching lines @@
   void SendScrollEnd(blink::WebGestureEvent update_event, bool synthetic);
   void SendScrollBegin(const blink::WebGestureEvent& gesture_update,
                        bool synthetic);
 
   MouseWheelEventQueueClient* client_;
   base::OneShotTimer scroll_end_timer_;
 
   std::deque<std::unique_ptr<QueuedWebMouseWheelEvent>> wheel_queue_;
   std::unique_ptr<QueuedWebMouseWheelEvent> event_sent_for_gesture_ack_;
 
-  // True if a non-synthetic GSB needs to be sent before a GSU is sent.
-  bool needs_scroll_begin_;
-
-  // True if a non-synthetic GSE needs to be sent because a non-synthetic
-  // GSB has been sent in the past.
-  bool needs_scroll_end_;
-
   // True if the touchpad and wheel scroll latching is enabled.
   bool enable_scroll_latching_;
 
   int64_t scroll_transaction_ms_;
   blink::WebGestureDevice scrolling_device_;
 
   DISALLOW_COPY_AND_ASSIGN(MouseWheelEventQueue);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_MOUSE_WHEEL_EVENT_QUEUE_H_