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 5204ba404803039e9d59ab83ec7eb32751902d76..0418d7f7b8c1fa5e836d669c2e4a421b6131f14b 100644
--- a/Source/core/testing/Internals.h
+++ b/Source/core/testing/Internals.h
@@ -59,6 +59,7 @@ 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;