code: function mergeComponentData (attrValue, extraData) {
    // Extra data not defined, just return attrValue.
    if (!extraData) { return attrValue; }
  
    // Merge multi-property data.
    if (extraData.constructor === Object) {
      return utils.extend(extraData, utils.styleParser.parse(attrValue || {}));
    }
  
    // Return data, precendence to the defined value.
    return attrValue || extraData;
  }
docs: Given entity defined value, merge in extra data if necessary.
  Handle both single and multi-property components.
  
  @param {string} attrValue - Entity data.
  @param extraData - Entity data from another source to merge in.