Refactor scroll chaining to use ScrollNodes without going through LayerImpl

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 86bc6581de31e99fc3d73299ed57783a4e62dd55..6df0b74af53b9fa3ee8807757291f0e3be575e9c 100644
--- a/cc/input/scroll_state.h
+++ b/cc/input/scroll_state.h
@@ -61,11 +61,10 @@ class CC_EXPORT ScrollState {
     data_.is_direct_manipulation = is_direct_manipulation;
   }
 
-  void set_scroll_chain_and_layer_tree(
-      const std::list<const ScrollNode*>& scroll_chain,
-      LayerTreeImpl* layer_tree_impl) {
+  void set_scroll_chain_and_layer_tree(std::list<ScrollNode*>* scroll_chain,

[bokan, 2017/02/21 19:33:39]

Nit, why pass by pointer rather than const-ref?

[pdr., 2017/02/22 21:35:59]

Good catch, this was just a mistake. I started removing consts and got carried
away. Fix up: https://codereview.chromium.org/2713713002

+                                       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) {
@@ -99,7 +98,7 @@ class CC_EXPORT ScrollState {
  private:
   ScrollStateData data_;
   LayerTreeImpl* layer_tree_impl_;
-  std::list<const ScrollNode*> scroll_chain_;
+  std::list<ScrollNode*> scroll_chain_;
 };
 
 }  // namespace cc