standardizeCSSValue = function(propertyName, value) {
  'use strict';
  var styleDeclaration = document.createElement('div').style;
  styleDeclaration[propertyName] = value;
  return styleDeclaration[propertyName];
}
Standardizes a CSS value for a given property by applying it to an element
and then reading it back.
@param {string} propertyName CSS property name.
@param {string} value CSS value.
@return {string} Normalized CSS value.