Coalesce async touch move events until the ack back from render

content/browser/renderer_host/input/mock_input_ack_handler.cc

Index: content/browser/renderer_host/input/mock_input_ack_handler.cc
diff --git a/content/browser/renderer_host/input/mock_input_ack_handler.cc b/content/browser/renderer_host/input/mock_input_ack_handler.cc
index 309280988555c29c7b20ce6de9a8caea65826e2a..5d983e31477fed9ed47a078a9db1d576b34d7462 100644
--- a/content/browser/renderer_host/input/mock_input_ack_handler.cc
+++ b/content/browser/renderer_host/input/mock_input_ack_handler.cc
@@ -47,6 +47,7 @@ void MockInputAckHandler::OnTouchEventAck(
     const TouchEventWithLatencyInfo& event,
     InputEventAckState ack_result) {
   VLOG(1) << __FUNCTION__ << " called!";
+  LOG(ERROR) << "   MockInputAckHandler::OnTouchEventAck   ";
   acked_touch_event_ = event;
   RecordAckCalled(event.event.type, ack_result);
   if (touch_followup_event_)