Add ImageLoader support for sizes based Client-Hints RW values

Source/core/html/HTMLImageElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * 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.
@@ skipping 89 matching lines @@
     virtual FloatSize defaultDestinationSize() const override;
     virtual const KURL& sourceURL() const override;
     virtual bool isOpaque() const override;
 
     // public so that HTMLPictureElement can call this as well.
     void selectSourceURL(ImageLoader::UpdateFromElementBehavior);
     void reattachFallbackContent();
     void setUseFallbackContent();
     void setIsFallbackImage() { m_isFallbackImage = true; }
 
+    float sourceSize(Element&);
+
 protected:
     explicit HTMLImageElement(Document&, HTMLFormElement* = 0, bool createdByParser = false);
 
     virtual void didMoveToNewDocument(Document& oldDocument) override;
     virtual bool useFallbackContent() const { return m_useFallbackContent; }
 
     virtual void didAddClosedShadowRoot(ShadowRoot&) override;
     virtual PassRefPtr<ComputedStyle> customStyleForLayoutObject() override;
 private:
     virtual bool areAuthorShadowsAllowed() const override { return false; }
@@ skipping 40 matching lines @@
     unsigned m_elementCreatedByParser : 1;
     // Intrinsic sizing is viewport dependant if the 'w' descriptor was used for the picked resource.
     unsigned m_intrinsicSizingViewportDependant : 1;
     unsigned m_useFallbackContent : 1;
     unsigned m_isFallbackImage : 1;
 };
 
 } // namespace blink
 
 #endif // HTMLImageElement_h