Introduce ES6 iterator for DOM objects.

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 0db3c83787b7ce6b76d5f41a3cc8420199863b8d..12cf46559f920143a7ccea399fd53e1e66301177 100644
--- a/Source/core/testing/Internals.h
+++ b/Source/core/testing/Internals.h
@@ -60,6 +60,7 @@ class HTMLMediaElement;
 class InternalProfilers;
 class InternalRuntimeFlags;
 class InternalSettings;
+class Iterator;
 class LayerRectList;
 class LocalFrame;
 class Node;
@@ -318,6 +319,8 @@ public:
 
     void forcePluginPlaceholder(HTMLElement* plugin, const String& htmlSource, ExceptionState&);
 
+    Iterator* iterator(ScriptState*, ExceptionState&);
+
 private:
     explicit Internals(Document*);
     Document* contextDocument() const;