Revert of Use Shadow DOM to display fallback content for images

Source/core/html/HTMLImageFallbackHelper.h

-/*
- * Copyright (C) 2014 Robert Hogan <robhogan@chromium.org>.
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Library General Public
- * License as published by the Free Software Foundation; either
- * version 2 of the License, or (at your option) any later version.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * Library General Public License for more details.
- *
- * You should have received a copy of the GNU Library General Public License
- * along with this library; see the file COPYING.LIB.  If not, write to
- * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
- * Boston, MA 02110-1301, USA.
- *
- */
-
-#ifndef HTMLImageFallbackHelper_h
-#define HTMLImageFallbackHelper_h
-
-#include "wtf/PassRefPtr.h"
-
-namespace blink {
-
-class Element;
-class RenderStyle;
-
-class HTMLImageFallbackHelper {
-public:
-    static void createAltTextShadowTree(Element&);
-    static PassRefPtr<RenderStyle> customStyleForAltText(Element&, PassRefPtr<RenderStyle> newStyle);
-};
-
-} // namespace blink
-
-#endif // HTMLImageFallbackHelper_h