Set the unique_event_id when converting from TouchEvent to WebTouchEvent

content/renderer/input/input_event_filter.cc

Index: content/renderer/input/input_event_filter.cc
diff --git a/content/renderer/input/input_event_filter.cc b/content/renderer/input/input_event_filter.cc
index 6c78d57b0213ecbfbc1ce152e3052783e466807c..818fae78fbef70ddc261e5c4a17dc75d13d4cd1f 100644
--- a/content/renderer/input/input_event_filter.cc
+++ b/content/renderer/input/input_event_filter.cc
@@ -182,6 +182,12 @@ void InputEventFilter::ForwardToHandler(const IPC::Message& message) {
   ack.state = ack_state;
   ack.latency = latency_info;
   ack.overscroll = overscroll_params.Pass();
+  if (WebInputEvent::isTouchEventType(ack.type)) {
+    const blink::WebTouchEvent& touch =
+        static_cast<const blink::WebTouchEvent&>(*event);
+    ack.unique_touch_event_id = touch.uniqueTouchEventId;
+  }
+
   SendMessage(scoped_ptr<IPC::Message>(
       new InputHostMsg_HandleInputEvent_ACK(routing_id, ack)));
 }