virtual void applyValue(CSSStyleSelector* selector, CSSValue* value) const
 {
     if (!value->isPrimitiveValue())
         return;
     CSSPrimitiveValue* primitiveValue = static_cast<CSSPrimitiveValue*>(value);
     FontDescription fontDescription = selector->fontDescription();
     switch (primitiveValue->getIdent()) {
     case CSSValueInvalid:
         ASSERT_NOT_REACHED();
         break;
     case CSSValueBolder:
         fontDescription.setWeight(fontDescription.bolderWeight());
         break;
     case CSSValueLighter:
         fontDescription.setWeight(fontDescription.lighterWeight());
         break;
     default:
         fontDescription.setWeight(*primitiveValue);
     }
     selector->setFontDescription(fontDescription);
 }