[Compositor event queue] Coalesce gesture scroll&pinch of the same sequence

ui/events/blink/blink_event_util.h

Index: ui/events/blink/blink_event_util.h
diff --git a/ui/events/blink/blink_event_util.h b/ui/events/blink/blink_event_util.h
index 5636d58b28511f0351c00c98d97ee86d628772f1..448e6412ee62cf67dd12f1c0d81e30b83322b630 100644
--- a/ui/events/blink/blink_event_util.h
+++ b/ui/events/blink/blink_event_util.h
@@ -33,6 +33,16 @@ bool CanCoalesce(const blink::WebInputEvent& event_to_coalesce,
 void Coalesce(const blink::WebInputEvent& event_to_coalesce,
               blink::WebInputEvent* event);
 
+bool IsCompatibleScrollorPinch(const blink::WebGestureEvent& new_event,
+                               const blink::WebGestureEvent& event_in_queue);
+
+// Coalesces 3 GestureScroll/PinchUpdate into 2 events.
+// Returns <GestureScrollUpdate, GesturePinchUpdate>.
+std::pair<blink::WebGestureEvent, blink::WebGestureEvent>
+CoalesceScrollAndPinch(const blink::WebGestureEvent* second_last_event,
+                       const blink::WebGestureEvent& last_event,
+                       const blink::WebGestureEvent& new_event);
+
 blink::WebTouchEvent CreateWebTouchEventFromMotionEvent(
     const MotionEvent& event,
     bool may_cause_scrolling);