message: fix shadowbox build on TS3
diff: export interface Clock {
  // Returns the current time in milliseconds from the epoch.
  now(): number;
  - setInterval(callback, intervalMs): number;
  + setInterval(callback, intervalMs): void;
  }
  export class RealClock implements Clock {
  - now(): number {
  + now() {
  return Date.now();
  }
  - setInterval(callback, intervalMs): number {
  - return setInterval(callback, intervalMs);
  + setInterval(callback, intervalMs) {
  + setInterval(callback, intervalMs);
  }
  }
  @@ -42,7 +42,6 @@ export class ManualClock implements Clock {
  setInterval(callback, intervalMs) {
  this.callbacks.push(callback);
  - return 0;
  }
  async runCallbacks() {
  