Refactor scroll chaining to use ScrollNodes without going through LayerImpl

cc/layers/layer_impl.cc

Index: cc/layers/layer_impl.cc
diff --git a/cc/layers/layer_impl.cc b/cc/layers/layer_impl.cc
index 4074061f723013ce0ad1ad8dfa7046dffc54ff04..891057fc48fccdad4a32f744ed70da5a4a21f5ad 100644
--- a/cc/layers/layer_impl.cc
+++ b/cc/layers/layer_impl.cc
@@ -133,12 +133,6 @@ void LayerImpl::SetDebugInfo(
   SetNeedsPushProperties();
 }
 
-void LayerImpl::DistributeScroll(ScrollState* scroll_state) {
-  ScrollTree& scroll_tree = GetScrollTree();
-  ScrollNode* scroll_node = scroll_tree.Node(scroll_tree_index());
-  scroll_tree.DistributeScroll(scroll_node, scroll_state);
-}
-
 void LayerImpl::SetTransformTreeIndex(int index) {
   transform_tree_index_ = index;
 }