Make sure <url>s are being serialized according to spec

third_party/WebKit/Source/core/css/CSSSVGDocumentValue.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 43 matching lines @@
 
         FetchRequest request(ResourceRequest(document->completeURL(m_url)), FetchInitiatorTypeNames::css);
         m_document = DocumentResource::fetchSVGDocument(request, document->fetcher());
     }
 
     return m_document.get();
 }
 
 String CSSSVGDocumentValue::customCSSText() const
 {
-    return quoteCSSStringIfNeeded(m_url);
+    return serializeString(m_url);
 }
 
 bool CSSSVGDocumentValue::equals(const CSSSVGDocumentValue& other) const
 {
     return m_url == other.m_url;
 }
 
 } // namespace blink