Revert "Revert 253606 "Revert 251238 "cc: Clean up iterator template to ...""

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index 5972a9f8303986a65849be5b35357767753d8066..bbcdee4bd6dbea7ca9a88c8de3799be62bda38a6 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -887,8 +887,12 @@ void LayerTreeHost::SetPrioritiesForSurfaces(size_t surface_memory_bytes) {
 
 void LayerTreeHost::SetPrioritiesForLayers(
     const RenderSurfaceLayerList& update_list) {
+  typedef LayerIterator<Layer,
+                        RenderSurfaceLayerList,
+                        RenderSurface,
+                        LayerIteratorActions::FrontToBack> LayerIteratorType;
+
   PriorityCalculator calculator;
-  typedef LayerIterator<Layer> LayerIteratorType;
   LayerIteratorType end = LayerIteratorType::End(&update_list);
   for (LayerIteratorType it = LayerIteratorType::Begin(&update_list);
        it != end;
@@ -985,6 +989,13 @@ void LayerTreeHost::PaintLayerContents(
     ResourceUpdateQueue* queue,
     bool* did_paint_content,
     bool* need_more_updates) {
+  // Use FrontToBack to allow for testing occlusion and performing culling
+  // during the tree walk.
+  typedef LayerIterator<Layer,
+                        RenderSurfaceLayerList,
+                        RenderSurface,
+                        LayerIteratorActions::FrontToBack> LayerIteratorType;
+
   bool record_metrics_for_frame =
       settings_.show_overdraw_in_tracing &&
       base::debug::TraceLog::GetInstance() &&
@@ -999,9 +1010,6 @@ void LayerTreeHost::PaintLayerContents(
 
   in_paint_layer_contents_ = true;
 
-  // Iterates front-to-back to allow for testing occlusion and performing
-  // culling during the tree walk.
-  typedef LayerIterator<Layer> LayerIteratorType;
   LayerIteratorType end = LayerIteratorType::End(&render_surface_layer_list);
   for (LayerIteratorType it =
            LayerIteratorType::Begin(&render_surface_layer_list);