Reconstitute const-ref parameter to set_scroll_chain_and_layer_tree

cc/input/scroll_state.h

Index: cc/input/scroll_state.h
diff --git a/cc/input/scroll_state.h b/cc/input/scroll_state.h
index 6df0b74af53b9fa3ee8807757291f0e3be575e9c..384a934fc22f55b57d97a58dc1e666ae719b94e1 100644
--- a/cc/input/scroll_state.h
+++ b/cc/input/scroll_state.h
@@ -61,10 +61,11 @@ class CC_EXPORT ScrollState {
     data_.is_direct_manipulation = is_direct_manipulation;
   }
 
-  void set_scroll_chain_and_layer_tree(std::list<ScrollNode*>* scroll_chain,
-                                       LayerTreeImpl* layer_tree_impl) {
+  void set_scroll_chain_and_layer_tree(
+      const std::list<ScrollNode*>& scroll_chain,
+      LayerTreeImpl* layer_tree_impl) {
     layer_tree_impl_ = layer_tree_impl;
-    scroll_chain_ = *scroll_chain;
+    scroll_chain_ = scroll_chain;
   }
 
   void set_current_native_scrolling_node(ScrollNode* scroll_node) {