Rethink PrivateName

closure.js

function observed({kind, key, placement, descriptor, initializer}, privateFieldMaker) {
  assert(kind == "field");
  assert(placement == "own");
  // Create a new anonymous private name as a key for a class element
  let { get, set } = privateFieldMaker();
  let underlyingDescriptor = { enumerable: false, configurable: false, writable: true };
  let underlying = { kind, key: storage, placement, descriptor: underlyingDescriptor, initializer };
  return {
    kind: "method",
    key,
    placement,
    descriptor: {
      get() { get(this); },
      set(value) {
        set(this, value);
        // Assume the @bound decorator was used on render
        window.requestAnimationFrame(this.render);
      },
      enumerable: descriptor.enumerable,
      configurable: descriptor.configurable,
    },
    extras: [underlying]
  };