Only allow change-of-basis between transform nodes on the same ancestor chain

cc/trees/property_tree.h

Index: cc/trees/property_tree.h
diff --git a/cc/trees/property_tree.h b/cc/trees/property_tree.h
index 00dc8d54ea5ed2426dd1d3dcc3d74130bb8afff1..6654c8f3a45dd99ee83f914fd40fe2692e8db36d 100644
--- a/cc/trees/property_tree.h
+++ b/cc/trees/property_tree.h
@@ -165,9 +165,6 @@ class CC_EXPORT TransformTree final : public PropertyTree<TransformNode> {
   // |anc_id|.
   bool IsDescendant(int desc_id, int anc_id) const;
 
-  // Returns the index of the lowest common ancestor of the nodes |a| and |b|.
-  int LowestCommonAncestor(int a, int b) const;
-
   // Computes the combined transform between |source_id| and |dest_id| and
   // returns false if the inverse of a singular transform was used. These two
   // nodes must be on the same ancestor chain.