Touchpad scroll latching enabled for Mac behind flag.

content/browser/renderer_host/input/mouse_wheel_event_queue.h

Index: content/browser/renderer_host/input/mouse_wheel_event_queue.h
diff --git a/content/browser/renderer_host/input/mouse_wheel_event_queue.h b/content/browser/renderer_host/input/mouse_wheel_event_queue.h
index 1f465b5051cd8f5d5218b4862d2c09276505f416..a9207fd08dfd5b94e65559206b10f61e42287ce9 100644
--- a/content/browser/renderer_host/input/mouse_wheel_event_queue.h
+++ b/content/browser/renderer_host/input/mouse_wheel_event_queue.h
@@ -80,7 +80,9 @@ class CONTENT_EXPORT MouseWheelEventQueue {
 
  private:
   void TryForwardNextEventToRenderer();
-  void SendScrollEnd(blink::WebGestureEvent update_event, bool synthetic);
+  void SendScrollEnd(blink::WebGestureEvent update_event,
+                     bool synthetic,
+                     bool may_precede_fling);
   void SendScrollBegin(const blink::WebGestureEvent& gesture_update,
                        bool synthetic);
 
@@ -103,6 +105,8 @@ class CONTENT_EXPORT MouseWheelEventQueue {
   int64_t scroll_transaction_ms_;
   blink::WebGestureDevice scrolling_device_;
 
+  blink::WebGestureEvent last_scroll_update_;
+
   DISALLOW_COPY_AND_ASSIGN(MouseWheelEventQueue);
 };