Remove ScrollNode's layer_id_to_scrollbars_enabled_map

cc/trees/property_tree.cc

Index: cc/trees/property_tree.cc
diff --git a/cc/trees/property_tree.cc b/cc/trees/property_tree.cc
index 9850577ff4ed778e9f6fd3ce8eb87e7cd57ef092..19a09e4172d27eaa74d7f268eb56b7def0063ca0 100644
--- a/cc/trees/property_tree.cc
+++ b/cc/trees/property_tree.cc
@@ -1142,8 +1142,6 @@ bool ScrollTree::operator==(const ScrollTree& other) const {
 #if DCHECK_IS_ON()
 void ScrollTree::CopyCompleteTreeState(const ScrollTree& other) {
   currently_scrolling_node_id_ = other.currently_scrolling_node_id_;
-  layer_id_to_scrollbars_enabled_map_ =
-      other.layer_id_to_scrollbars_enabled_map_;
   layer_id_to_scroll_offset_map_ = other.layer_id_to_scroll_offset_map_;
   layer_id_to_synced_scroll_offset_map_ =
       other.layer_id_to_synced_scroll_offset_map_;