cc: Remove map lookup from RenderSurfaceImpl::EffectTreeIndex

cc/layers/render_surface_impl.cc

Index: cc/layers/render_surface_impl.cc
diff --git a/cc/layers/render_surface_impl.cc b/cc/layers/render_surface_impl.cc
index 9c980a2f5b11051c633fd8c6d61219d640f0c58f..a92e21b14c50d44ae7be26c5c2d09052fcf8c6e3 100644
--- a/cc/layers/render_surface_impl.cc
+++ b/cc/layers/render_surface_impl.cc
@@ -35,6 +35,7 @@ RenderSurfaceImpl::RenderSurfaceImpl(LayerImpl* owning_layer)
     : owning_layer_(owning_layer),
       layer_tree_impl_(owning_layer->layer_tree_impl()),
       stable_effect_id_(owning_layer->id()),
+      effect_tree_index_(EffectTree::kInvalidNodeId),
       surface_property_changed_(false),
       ancestor_property_changed_(false),
       contributes_to_drawn_surface_(false),
@@ -159,8 +160,10 @@ int RenderSurfaceImpl::ClipTreeIndex() const {
 }
 
 int RenderSurfaceImpl::EffectTreeIndex() const {
-  return layer_tree_impl_->property_trees()
-      ->effect_id_to_index_map[stable_effect_id_];
+  DCHECK_EQ(effect_tree_index_,
+            layer_tree_impl_->property_trees()
+                ->effect_id_to_index_map[stable_effect_id_]);
+  return effect_tree_index_;
 }
 
 const EffectNode* RenderSurfaceImpl::OwningEffectNode() const {