Set proper referrer for css resource fetching

Source/core/css/CSSImageValue.h

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2008, 2012 Apple 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 35 matching lines @@
     }
     ~CSSImageValue();
 
     StyleFetchedImage* cachedImage(ResourceFetcher*, const ResourceLoaderOptions&);
     StyleFetchedImage* cachedImage(ResourceFetcher* fetcher) { return cachedImage(fetcher, ResourceFetcher::defaultResourceOptions()); }
     // Returns a StyleFetchedImage if the image is cached already, otherwise a StylePendingImage.
     StyleImage* cachedOrPendingImage();
 
     const String& url() { return m_absoluteURL; }
 
+    void setReferrer(const String& referrer) { m_referrer = referrer; }
+    const String& referrer() { return m_referrer; }
+
     void reResolveURL(const Document&);
 
     String customCSSText() const;
 
     PassRefPtrWillBeRawPtr<CSSValue> cloneForCSSOM() const;
 
     bool hasFailedOrCanceledSubresources() const;
 
     bool equals(const CSSImageValue&) const;
 
     bool knownToBeOpaque(const RenderObject*) const;
 
     void setInitiator(const AtomicString& name) { m_initiatorName = name; }
 
     void traceAfterDispatch(Visitor*);
 
 private:
     CSSImageValue(const String& rawValue, const KURL&, StyleImage*);
 
     String m_relativeURL;
     String m_absoluteURL;
+    String m_referrer;
     RefPtr<StyleImage> m_image;
     bool m_accessedImage;
     AtomicString m_initiatorName;
 };
 
 DEFINE_CSS_VALUE_TYPE_CASTS(CSSImageValue, isImageValue());
 
 } // namespace WebCore
 
 #endif // CSSImageValue_h