Add the NonElementParentNode interface

Source/core/dom/NonElementParentNode.h

Index: Source/core/dom/NonElementParentNode.h
diff --git a/Source/core/dom/NonElementParentNode.h b/Source/core/dom/NonElementParentNode.h
new file mode 100644
index 0000000000000000000000000000000000000000..f9989642a476480602f171da8d75c45490423423
--- /dev/null
+++ b/Source/core/dom/NonElementParentNode.h
@@ -0,0 +1,28 @@
+// Copyright 2015 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 NonElementParentNode_h
+#define NonElementParentNode_h
+
+#include "core/dom/Document.h"
+#include "core/dom/DocumentFragment.h"
+
+namespace blink {
+
+class NonElementParentNode {
+public:
+    static Element* getElementById(Document& document, const AtomicString& id)
+    {
+        return document.getElementById(id);
+    }
+
+    static Element* getElementById(DocumentFragment& fragment, const AtomicString& id)
+    {
+        return fragment.getElementById(id);
+    }
+};
+
+} // namespace blink
+
+#endif // NonElementParentNode_h