Fix serialization of content property to always quote

Source/core/css/CSSValueList.cpp

Index: Source/core/css/CSSValueList.cpp
diff --git a/Source/core/css/CSSValueList.cpp b/Source/core/css/CSSValueList.cpp
index cb6bd1428ccd8f2eaaeabb87847fbec72773f46a..eb181f646f014e4a1f3cb06a12d654942f0f7b35 100644
--- a/Source/core/css/CSSValueList.cpp
+++ b/Source/core/css/CSSValueList.cpp
@@ -83,7 +83,7 @@ PassRefPtrWillBeRawPtr<CSSValueList> CSSValueList::copy()
     return newList.release();
 }
 
-String CSSValueList::customCSSText(CSSTextFormattingFlags formattingFlag) const
+String CSSValueList::customCSSText() const
 {
     StringBuilder result;
     String separator;
@@ -105,10 +105,7 @@ String CSSValueList::customCSSText(CSSTextFormattingFlags formattingFlag) const
     for (unsigned i = 0; i < size; i++) {
         if (!result.isEmpty())
             result.append(separator);
-        if (formattingFlag == AlwaysQuoteCSSString && m_values[i]->isPrimitiveValue())
-            result.append(toCSSPrimitiveValue(m_values[i].get())->customCSSText(AlwaysQuoteCSSString));
-        else
-            result.append(m_values[i]->cssText());
+        result.append(m_values[i]->cssText());
     }
 
     return result.toString();