[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..8759205500a4b915dd116e364f870e9d1de09ab6 100644
--- a/ui/events/blink/blink_event_util.h
+++ b/ui/events/blink/blink_event_util.h
@@ -7,12 +7,11 @@
 
 #include <memory>
 
+#include "third_party/WebKit/public/platform/WebGestureEvent.h"
 #include "third_party/WebKit/public/platform/WebInputEvent.h"
 #include "ui/events/gesture_detection/motion_event.h"
 
 namespace blink {
-class WebGestureEvent;
-class WebInputEvent;
 class WebTouchEvent;
 }
 
@@ -33,6 +32,16 @@ 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);
@@ -84,6 +93,18 @@ bool IsGestureScollOrPinch(blink::WebInputEvent::Type);
 
 bool IsContinuousGestureEvent(blink::WebInputEvent::Type);
 
+inline const blink::WebGestureEvent* ToWebGestureEvent(

[tdresser, 2016/12/13 17:18:19]

The asymmetry of these methods is a bit tricky. Could we make it so neither or
both of them take a pointer?

[chongz, 2016/12/13 18:55:45]

Removed the pointer version. 
However I'm not entirely sure if that's what you mean because both methods are
converting |WebInputEvent| to |WebGestureEvent|.

+    const blink::WebInputEvent* event) {
+  DCHECK(!event || IsGestureScollOrPinch(event->type));
+  return static_cast<const blink::WebGestureEvent*>(event);
+}
+
+inline const blink::WebGestureEvent& ToWebGestureEvent(
+    const blink::WebInputEvent& event) {
+  DCHECK(IsGestureScollOrPinch(event.type));
+  return static_cast<const blink::WebGestureEvent&>(event);
+}
+
 }  // namespace ui
 
 #endif  // UI_EVENTS_BLINK_BLINK_EVENT_UTIL_H_