operator property
      
      CSSMathOperator
      get
      operator
      
    
    
The CSSMathValue.operator read-only
property of the CSSMathValue interface indicates the operator that the
current subtype represents. For example, if the current CSSMathValue
subtype is CSSMathSum, this property will return the string
"sum".
Implementation
external CSSMathOperator get operator;