Introduce ES6 iterator for DOM objects.

Source/core/dom/Iterator.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef Iterator_h
+#define Iterator_h
+
+#include "bindings/core/v8/ScriptValue.h"
+#include "bindings/core/v8/ScriptWrappable.h"
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class ExceptionState;
+
+class Iterator : public GarbageCollectedFinalized<Iterator>, public ScriptWrappable {
+    DEFINE_WRAPPERTYPEINFO();
+public:
+    Iterator() { ScriptWrappable::init(this); }
+    virtual ~Iterator() { }
+
+    virtual ScriptValue next(ScriptState*, ExceptionState&) = 0;
+    virtual ScriptValue next(ScriptState*, ScriptValue /* value */, ExceptionState&) = 0;
+    Iterator* iterator(ScriptState*, ExceptionState&) { return this; }
+
+    virtual void trace(Visitor*) { }
+};
+
+} // namespace blink
+
+#endif
+