Consolidate WebInputEvent coalescing logic

content/browser/renderer_host/input/gesture_event_filter.cc

Index: content/browser/renderer_host/input/gesture_event_filter.cc
diff --git a/content/browser/renderer_host/input/gesture_event_filter.cc b/content/browser/renderer_host/input/gesture_event_filter.cc
index 8639043edd6766a4f1f377cc371ac6d16a1a19c3..60bb6a66ece2acf8948e07a8a47dabce4dcfe530 100644
--- a/content/browser/renderer_host/input/gesture_event_filter.cc
+++ b/content/browser/renderer_host/input/gesture_event_filter.cc
@@ -373,16 +373,11 @@ void GestureEventFilter::MergeOrInsertScrollAndPinchEvent(
     return;
   }
   GestureEventWithLatencyInfo* last_event = &coalesced_gesture_events_.back();
-  if (gesture_event.event.type == WebInputEvent::GestureScrollUpdate &&
-      last_event->event.type == WebInputEvent::GestureScrollUpdate &&
-      last_event->event.modifiers == gesture_event.event.modifiers) {
-    last_event->event.data.scrollUpdate.deltaX +=
-        gesture_event.event.data.scrollUpdate.deltaX;
-    last_event->event.data.scrollUpdate.deltaY +=
-        gesture_event.event.data.scrollUpdate.deltaY;
-    last_event->latency.MergeWith(gesture_event.latency);
+  if (last_event->CanCoalesceWith(gesture_event)) {
+    last_event->CoalesceWith(gesture_event);
     return;
   }
+
   if (coalesced_gesture_events_.size() == 2 ||
       (coalesced_gesture_events_.size() == 3 && ignore_next_ack_) ||
       !ShouldTryMerging(gesture_event, *last_event)) {