code: function() {
              if (observed.size) {
                  observed.forEach(performPropertyChecks);
                  handlers.forEach(deliverHandlerRecords);
                  nextFrame(runGlobalLoop);
              }
          }
docs: Functions for internal usage 
  Checks if the argument is an Array object. Polyfills Array.isArray.
  @function isArray
  @param {?*} object
  @returns {Boolean}