cc: Compute target space transform dynamically

cc/layers/layer.cc

Index: cc/layers/layer.cc
diff --git a/cc/layers/layer.cc b/cc/layers/layer.cc
index e0e09b5d630c48532175ed6f7c0177344743c140..36d725c6010a8e87e36eb02bab050783d74e9d84 100644
--- a/cc/layers/layer.cc
+++ b/cc/layers/layer.cc
@@ -981,6 +981,15 @@ int Layer::effect_tree_index() const {
   return effect_tree_index_;
 }
 
+int Layer::render_target_effect_tree_index() const {
+  EffectNode* effect_node =
+      layer_tree_host_->property_trees()->effect_tree.Node(effect_tree_index_);
+  if (effect_node->has_render_surface)
+    return effect_node->id;
+  else
+    return effect_node->target_id;
+}
+
 void Layer::SetScrollTreeIndex(int index) {
   DCHECK(IsPropertyChangeAllowed());
   if (scroll_tree_index_ == index)