Async Wheel Event with only the first one cancellable behind a flag.

ui/events/blink/blink_event_util.cc

 // Copyright 2015 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.
 
 // MSVC++ requires this to be set before any other includes to get M_PI.
 #define _USE_MATH_DEFINES
 
 #include "ui/events/blink/blink_event_util.h"
 
 #include <stddef.h>
@@ skipping 245 matching lines @@
 }
 
 bool CanCoalesce(const WebMouseWheelEvent& event_to_coalesce,
                  const WebMouseWheelEvent& event) {
   return event.GetModifiers() == event_to_coalesce.GetModifiers() &&
          event.scroll_by_page == event_to_coalesce.scroll_by_page &&
          event.phase == event_to_coalesce.phase &&
          event.momentum_phase == event_to_coalesce.momentum_phase &&
          event.resending_plugin_id == event_to_coalesce.resending_plugin_id &&
          event.has_precise_scrolling_deltas ==
-             event_to_coalesce.has_precise_scrolling_deltas;
+             event_to_coalesce.has_precise_scrolling_deltas &&
+         event.dispatch_type == event_to_coalesce.dispatch_type;

[dtapuska, 2017/06/16 17:36:09]

This seems wrong.

For touch we allow a cancellable touch move to be coalesced with a
non-cancellable one. 

I think the preferred solution is something like:
https://cs.chromium.org/chromium/src/ui/events/blink/blink_event_util.cc?l=344

[sahel, 2017/06/20 19:22:33]

Done.

 }
 
 void Coalesce(const WebMouseWheelEvent& event_to_coalesce,
               WebMouseWheelEvent* event) {
   DCHECK(CanCoalesce(event_to_coalesce, *event));
   float unaccelerated_x =
       GetUnacceleratedDelta(event->delta_x, event->acceleration_ratio_x) +
       GetUnacceleratedDelta(event_to_coalesce.delta_x,
                             event_to_coalesce.acceleration_ratio_x);
   float unaccelerated_y =
@@ skipping 706 matching lines @@
   switch (type) {
     case blink::WebGestureEvent::kGestureScrollUpdate:
     case blink::WebGestureEvent::kGesturePinchUpdate:
       return true;
     default:
       return false;
   }
 }
 
 }  // namespace ui