Use Shadow DOM to display fallback content for images

Source/core/html/HTMLImageFallbackHelper.h

 /*

[pdr., 2014/11/14 07:34:17]

For new files the lawyercats have asked that we just use the small copyright
header (http://www.chromium.org/developers/coding-style#TOC-File-headers)

// 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.

(Here, and HTMLImageFallbackHelper.cpp)

- * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
- *           (C) 1999 Antti Koivisto (koivisto@kde.org)
- * Copyright (C) 2010 Apple Inc. All rights reserved.
+ * 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 HTMLMenuElement_h
-#define HTMLMenuElement_h
+#ifndef HTMLImageFallbackHelper_h
+#define HTMLImageFallbackHelper_h
 
-#include "core/html/HTMLElement.h"
+#include "wtf/PassRefPtr.h"
 
 namespace blink {
 
-class HTMLMenuElement final : public HTMLElement {
-    DEFINE_WRAPPERTYPEINFO();
+class Element;
+class RenderStyle;
+
+class HTMLImageFallbackHelper {
 public:
-    DECLARE_NODE_FACTORY(HTMLMenuElement);
-
-private:
-    explicit HTMLMenuElement(Document&);
+    static void createAltTextShadowTree(Element&);
+    static PassRefPtr<RenderStyle> customStyleForAltText(Element&, PassRefPtr<RenderStyle> newStyle);
 };
 
 } // namespace blink
 
-#endif // HTMLMenuElement_h
+#endif // HTMLImageFallbackHelper_h