Fix serialization of content property to always quote

Source/core/css/parser/CSSPropertyParser.cpp

Index: Source/core/css/parser/CSSPropertyParser.cpp
diff --git a/Source/core/css/parser/CSSPropertyParser.cpp b/Source/core/css/parser/CSSPropertyParser.cpp
index 68300c70665e606921cde5d9489b7f27b538a455..5c521e86e04df9bac4ea6aee5c7c50f6f02abf3d 100644
--- a/Source/core/css/parser/CSSPropertyParser.cpp
+++ b/Source/core/css/parser/CSSPropertyParser.cpp
@@ -320,10 +320,10 @@ PassRefPtrWillBeRawPtr<CSSPrimitiveValue> CSSPropertyParser::createPrimitiveNume
     return cssValuePool().createValue(value->fValue, static_cast<CSSPrimitiveValue::UnitType>(value->unit));
 }
 
-inline PassRefPtrWillBeRawPtr<CSSPrimitiveValue> CSSPropertyParser::createPrimitiveStringValue(CSSParserValue* value)
+inline PassRefPtrWillBeRawPtr<CSSPrimitiveValue> CSSPropertyParser::createPrimitiveStringValue(CSSParserValue* value, CSSPrimitiveValue::UnitType type)
 {
     ASSERT(value->unit == CSSPrimitiveValue::CSS_STRING || value->unit == CSSPrimitiveValue::CSS_IDENT);
-    return cssValuePool().createValue(value->string, CSSPrimitiveValue::CSS_STRING);
+    return cssValuePool().createValue(value->string, type);
 }
 
 inline PassRefPtrWillBeRawPtr<CSSValue> CSSPropertyParser::createCSSImageValueWithReferrer(const String& rawValue, const KURL& url)
@@ -2221,7 +2221,7 @@ bool CSSPropertyParser::parseContent(CSSPropertyID propId, bool important)
                 break;
             }
         } else if (val->unit == CSSPrimitiveValue::CSS_STRING) {
-            parsedValue = createPrimitiveStringValue(val);
+            parsedValue = createPrimitiveStringValue(val, CSSPrimitiveValue::CSS_STRING);
         }
         if (!parsedValue)
             break;
@@ -3263,7 +3263,7 @@ PassRefPtrWillBeRawPtr<CSSValue> CSSPropertyParser::parseGridPosition()
 
     // For the <custom-ident> case.
     if (gridLineName && !numericValue && !hasSeenSpanKeyword)
-        return cssValuePool().createValue(gridLineName->getStringValue(), CSSPrimitiveValue::CSS_STRING);
+        return cssValuePool().createValue(gridLineName->getStringValue(), CSSPrimitiveValue::CSS_CUSTOM_IDENT);
 
     RefPtrWillBeRawPtr<CSSValueList> values = CSSValueList::createSpaceSeparated();
     if (hasSeenSpanKeyword)
@@ -3851,7 +3851,7 @@ PassRefPtrWillBeRawPtr<CSSValue> CSSPropertyParser::parseCounterContent(CSSParse
 
     RefPtrWillBeRawPtr<CSSPrimitiveValue> separator = nullptr;
     if (!counters)
-        separator = cssValuePool().createValue(String(), CSSPrimitiveValue::CSS_STRING);
+        separator = cssValuePool().createValue(String(), CSSPrimitiveValue::CSS_CUSTOM_IDENT);
     else {
         args->next();
         if (!consumeComma(args))