cc: Compute target space transform dynamically

cc/layers/layer.h

Index: cc/layers/layer.h
diff --git a/cc/layers/layer.h b/cc/layers/layer.h
index 711ae7152848cdf6c9951ece43f9f6c97303cba1..261ccbbbdc88eccb448a6f80b51ea56a76589a34 100644
--- a/cc/layers/layer.h
+++ b/cc/layers/layer.h
@@ -430,6 +430,10 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
   void SetEffectTreeIndex(int index);
   int effect_tree_index() const;
 
+  // TODO(sunxd): Remove this when we do not compute target space transforms on
+  // main thread in tests.
+  int render_target_effect_tree_index() const;
+
   void SetScrollTreeIndex(int index);
   int scroll_tree_index() const;