Set proper referrer for css resource fetching

Source/core/css/CSSImageValue.h

Index: Source/core/css/CSSImageValue.h
diff --git a/Source/core/css/CSSImageValue.h b/Source/core/css/CSSImageValue.h
index 2d0c1e903d5cb05713a91b9519f52aa091758964..20c0564779a935ac98858f4458c11c41ed70d973 100644
--- a/Source/core/css/CSSImageValue.h
+++ b/Source/core/css/CSSImageValue.h
@@ -53,6 +53,9 @@ public:
 
     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;
@@ -74,6 +77,7 @@ private:
 
     String m_relativeURL;
     String m_absoluteURL;
+    String m_referrer;
     RefPtr<StyleImage> m_image;
     bool m_accessedImage;
     AtomicString m_initiatorName;