Find root scroll layer at tree activation

cc/layer_tree_impl.h

Index: cc/layer_tree_impl.h
diff --git a/cc/layer_tree_impl.h b/cc/layer_tree_impl.h
index e83647b57f4a9cc5bd137f636da1731309cf047c..284e9bc2f47f905bc796cabe5c3611953e68f551 100644
--- a/cc/layer_tree_impl.h
+++ b/cc/layer_tree_impl.h
@@ -30,6 +30,7 @@ class LayerTreeImpl;
 class LayerTreeSettings;
 class OutputSurface;
 class PinchZoomViewport;
+class Proxy;
 class ResourceProvider;
 class TileManager;
 
@@ -88,18 +89,12 @@ class CC_EXPORT LayerTreeImpl {
     hud_layer_ = layer_impl;
   }
 
-  LayerImpl* root_scroll_layer() { return root_scroll_layer_; }
-  const LayerImpl* root_scroll_layer() const { return root_scroll_layer_; }
-  void set_root_scroll_layer(LayerImpl* layer_impl) {
-    root_scroll_layer_ = layer_impl;
+  LayerImpl* RootScrollLayer();
+  LayerImpl* CurrentlyScrollingLayer();
+  void set_currently_scrolling_layer(LayerImpl* layer) {
+    currently_scrolling_layer_ = layer;
   }
 
-  LayerImpl* currently_scrolling_layer() { return currently_scrolling_layer_; }
-  void set_currently_scrolling_layer(LayerImpl* layer_impl) {
-    currently_scrolling_layer_ = layer_impl;
-  }
-
-  void FindRootScrollLayer();
   void ClearCurrentlyScrollingLayer();
 
   void UpdateMaxScrollOffset();
@@ -140,6 +135,8 @@ class CC_EXPORT LayerTreeImpl {
 protected:
   LayerTreeImpl(LayerTreeHostImpl* layer_tree_host_impl);
 
+  void FindRootScrollLayer();
+
   LayerTreeHostImpl* layer_tree_host_impl_;
   int source_frame_number_;
   scoped_ptr<LayerImpl> root_layer_;