Revert of Use Shadow DOM to display fallback content for images

Source/core/html/HTMLImageFallbackHelper.h

Index: Source/core/html/HTMLImageFallbackHelper.h
diff --git a/Source/core/html/HTMLImageFallbackHelper.h b/Source/core/html/HTMLImageFallbackHelper.h
deleted file mode 100644
index f73a304c4b248e4969faada744fe2f3358880618..0000000000000000000000000000000000000000
--- a/Source/core/html/HTMLImageFallbackHelper.h
+++ /dev/null
@@ -1,23 +0,0 @@
-// 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 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