GetOwnerDocument should return NS_ERROR_NOT_IMPLEMENTED if it's not going to modify its input

content/base/src/nsGenericElement.cpp

@@ -287,7 +287,7 @@ NS_IMETHODIMP
 nsDOMAttribute::GetOwnerDocument(nsIDOMDocument** aOwnerDocument)
 {
   // XXX TBI
-  return NS_OK;
+  return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 //----------------------------------------------------------------------

layout/base/src/nsGenericElement.cpp

@@ -287,7 +287,7 @@ NS_IMETHODIMP
 nsDOMAttribute::GetOwnerDocument(nsIDOMDocument** aOwnerDocument)
 {
   // XXX TBI
-  return NS_OK;
+  return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 //----------------------------------------------------------------------