Add an intermediate function to generate 2 paint-order lists.

Source/core/testing/Internals.h

Index: Source/core/testing/Internals.h
diff --git a/Source/core/testing/Internals.h b/Source/core/testing/Internals.h
index cab8ffb94e990b3a0924d537bfac3cf529cab123..96fd6147bd6a504dc08fa10243a3a3662f6920f1 100644
--- a/Source/core/testing/Internals.h
+++ b/Source/core/testing/Internals.h
@@ -217,6 +217,10 @@ public:
     };
     String layerTreeAsText(Document*, unsigned flags, ExceptionCode&) const;
     String layerTreeAsText(Document*, ExceptionCode&) const;
+
+    PassRefPtr<NodeList> paintOrderListBeforePromote(Element* element, ExceptionCode& ec);
+    PassRefPtr<NodeList> paintOrderListAfterPromote(Element* element, ExceptionCode& ec);
+
     String repaintRectsAsText(Document*, ExceptionCode&) const;
     String scrollingStateTreeAsText(Document*, ExceptionCode&) const;
     String mainThreadScrollingReasons(Document*, ExceptionCode&) const;