Touchpad scroll latching enabled for Mac behind flag.

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 62 matching lines @@
     return !wheel_queue_.empty() || event_sent_for_gesture_ack_;
   }
 
   size_t queued_size() const { return wheel_queue_.size(); }
   bool event_in_flight() const {
     return event_sent_for_gesture_ack_ != nullptr;
   }
 
  private:
   void TryForwardNextEventToRenderer();
-  void SendScrollEnd(blink::WebGestureEvent update_event, bool synthetic);
+  void SendScrollEnd(blink::WebGestureEvent update_event,
+                     bool synthetic,
+                     bool fling_might_happen_next);

[tdresser, 2016/11/14 16:02:29]

Can we be consistent, and call this may_precede_fling as well?

[sahel, 2016/11/18 16:13:58]

Done.

   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_;
 
+  blink::WebGestureEvent last_scroll_update_;
+
   DISALLOW_COPY_AND_ASSIGN(MouseWheelEventQueue);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_MOUSE_WHEEL_EVENT_QUEUE_H_