Remove remaining HTML elements

sky/engine/core/html/HTMLImportElement.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 SKY_ENGINE_CORE_HTML_HTMLIMPORTELEMENT_H_
-#define SKY_ENGINE_CORE_HTML_HTMLIMPORTELEMENT_H_
-
-#include "sky/engine/core/html/HTMLElement.h"
-#include "sky/engine/core/html/imports/HTMLImportChildClient.h"
-
-namespace blink {
-
-class HTMLImportElement final : public HTMLElement, public HTMLImportChildClient {
-    DEFINE_WRAPPERTYPEINFO();
-public:
-    static PassRefPtr<HTMLImportElement> create(Document&);
-
-private:
-    explicit HTMLImportElement(Document&);
-    ~HTMLImportElement();
-
-    bool shouldLoad() const;
-    void load();
-
-    // From HTMLElement
-    void insertedInto(ContainerNode*) override;
-
-    // From HTMLImportChildClient
-    void didFinish() override;
-    void importChildWasDestroyed(HTMLImportChild*) override;
-    bool isSync() const override;
-    Element* link() override;
-
-    HTMLImportChild* m_child;
-};
-
-} // namespace blink
-
-#endif  // SKY_ENGINE_CORE_HTML_HTMLIMPORTELEMENT_H_