Stylesheet rule.cssText of content property should be quoted when the value is string.

Source/core/css/CSSPrimitiveValue.h

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  *
  * 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 286 matching lines @@
 
     CSSBasicShape* getShapeValue() const { return m_primitiveUnitType != CSS_SHAPE ? 0 : m_value.shape; }
     
     CSSCalcValue* cssCalcValue() const { return m_primitiveUnitType != CSS_CALC ? 0 : m_value.calc; }
 
     CSSPropertyID getPropertyID() const { return m_primitiveUnitType == CSS_PROPERTY_ID ? m_value.propertyID : CSSPropertyInvalid; }
     CSSValueID getValueID() const { return m_primitiveUnitType == CSS_VALUE_ID ? m_value.valueID : CSSValueInvalid; }
 
     template<typename T> inline operator T() const; // Defined in CSSPrimitiveValueMappings.h
 
-    String customCssText() const;
+    String customCssText(CssTextFormattingFlags = QuoteCSSStringIfNeeded) const;
     String customSerializeResolvingVariables(const HashMap<AtomicString, String>&) const;
     bool hasVariableReference() const;
 
     bool isQuirkValue() { return m_isQuirkValue; }
 
     void addSubresourceStyleURLs(ListHashSet<KURL>&, const StyleSheetContents*) const;
 
     Length viewportPercentageLength();
     
     PassRefPtr<CSSPrimitiveValue> cloneForCSSOM() const;
@@ skipping 69 matching lines @@
     ASSERT_WITH_SECURITY_IMPLICATION(!value || value->isPrimitiveValue());
     return static_cast<const CSSPrimitiveValue*>(value);
 }
 
 // Catch unneeded cast.
 void toCSSPrimitiveValue(const CSSPrimitiveValue*);
 
 } // namespace WebCore
 
 #endif // CSSPrimitiveValue_h