Ignore the rest of the scroll sequence if GSB is ignored.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 435cc8d21fe0f21e9e70a8feedda979c708e8aa8..2209c4181aea306ef4dd53354c17075dc8898d09 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -2773,6 +2773,8 @@ InputHandler::ScrollStatus LayerTreeHostImpl::ScrollBeginImpl(
       MainThreadScrollingReason::kNotScrollingOnMain;
   if (!scrolling_node) {
     scroll_status.thread = SCROLL_IGNORED;
+    if (settings_.is_layer_tree_for_subframe)
+      scroll_status.thread = SCROLL_UNKNOWN;
     scroll_status.main_thread_scrolling_reasons =
         MainThreadScrollingReason::kNoScrollingLayer;
     return scroll_status;