Fix serialization of content property to always quote

Source/core/css/parser/CSSPropertyParser.h

 /*
  * Copyright (C) 2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 - 2010  Torch Mobile (Beijing) Co. Ltd. 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 255 matching lines @@
 
     bool parseFontFeatureTag(CSSValueList*);
     PassRefPtrWillBeRawPtr<CSSValue> parseFontFeatureSettings();
 
     bool parseFontVariantLigatures(bool important);
 
     bool parseGeneratedImage(CSSParserValueList*, RefPtrWillBeRawPtr<CSSValue>&);
 
     PassRefPtrWillBeRawPtr<CSSPrimitiveValue> createPrimitiveNumericValue(CSSParserValue*);
     PassRefPtrWillBeRawPtr<CSSPrimitiveValue> createPrimitiveStringValue(CSSParserValue*);
+    PassRefPtrWillBeRawPtr<CSSPrimitiveValue> createPrimitiveCustomIdentValue(CSSParserValue*);
 
     PassRefPtrWillBeRawPtr<CSSValue> createCSSImageValueWithReferrer(const String& rawValue, const KURL&);
 
     PassRefPtrWillBeRawPtr<CSSBasicShape> parseInsetRoundedCorners(PassRefPtrWillBeRawPtr<CSSBasicShapeInset>, CSSParserValueList*);
 
     enum SizeParameterType {
         None,
         Auto,
         Length,
         PageSize,
@@ skipping 90 matching lines @@
     RefPtrWillBeMember<CSSCalcValue> m_parsedCalculation;
 };
 
 CSSPropertyID cssPropertyID(const CSSParserString&);
 CSSPropertyID cssPropertyID(const String&);
 CSSValueID cssValueKeywordID(const CSSParserString&);
 
 } // namespace blink
 
 #endif // CSSPropertyParser_h