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

Source/core/css/CSSImageValue.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2008 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 90 matching lines @@
     return true;
 }
 
 bool CSSImageValue::equals(const CSSImageValue& other) const
 {
     return m_absoluteURL == other.m_absoluteURL;
 }
 
 String CSSImageValue::customCSSText() const
 {
-    // TODO(nainar): Serialise with quotation marks to match spec: https://drafts.csswg.org/cssom/#serialize-a-url
-    return "url(" + quoteCSSURLIfNeeded(serializeStringWithoutQuotations(m_relativeURL)) + ")";
+    return "url(" + serializeString(m_relativeURL) + ")";
 }
 
 bool CSSImageValue::knownToBeOpaque(const LayoutObject* layoutObject) const
 {
     return m_image ? m_image->knownToBeOpaque(layoutObject) : false;
 }
 
 DEFINE_TRACE_AFTER_DISPATCH(CSSImageValue)
 {
     visitor->trace(m_image);
     CSSValue::traceAfterDispatch(visitor);
 }
 
 void CSSImageValue::reResolveURL(const Document& document)
 {
     KURL url = document.completeURL(m_relativeURL);
     if (url == m_absoluteURL)
         return;
     m_absoluteURL = url.string();
     m_accessedImage = false;
     m_image.clear();
 }
 
 } // namespace blink