Coalesce async touch move events until the ack back from render

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 180be389354052d41f59adf08e1000f71da72ef9..a5c1cee8a5aa51cd516596a5d8cbae87c18dd75b 100644
--- a/content/renderer/input/input_event_filter.cc
+++ b/content/renderer/input/input_event_filter.cc
@@ -150,7 +150,7 @@ void InputEventFilter::ForwardToHandler(const IPC::Message& message) {
   bool is_keyboard_shortcut = get<2>(params);
   DCHECK(event);
 
-  const bool send_ack = !WebInputEventTraits::IgnoresAckDisposition(*event);
+  const bool send_ack = WebInputEventTraits::WillReceiveAckFromRenderer(*event);
 
   // Intercept |DidOverscroll| notifications, bundling any triggered overscroll
   // response with the input event ack.
@@ -181,6 +181,8 @@ void InputEventFilter::ForwardToHandler(const IPC::Message& message) {
   ack.state = ack_state;
   ack.latency = latency_info;
   ack.overscroll = overscroll_params.Pass();
+  ack.unique_touch_event_id =
+      WebInputEventTraits::GetUniqueTouchEventId(*event);
   SendMessage(scoped_ptr<IPC::Message>(
       new InputHostMsg_HandleInputEvent_ACK(routing_id, ack)));
 }