@Override
    public String toString() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.toString();
    }

    @Override
    public boolean equals(@Nullable Object o) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.equals(o);
    }

    @Override
    public int hashCode() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.hashCode();
    }

     * The URL that failed during crawling.
     * This is a required field containing the actual URL that encountered an error.
     */
    @Required
    public String url;

    /**
     * The name of the crawler thread that encountered the failure.
     * This is a required field used for identifying which crawler process failed.
     */
    @Required
    public String threadName;

    /**

    @Override
    public boolean offer(E o) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.offer(o);
    }

    @Override
    public @Nullable E poll() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.poll();
    }

    @Override
    public E remove() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.remove();
    }

    @Override

   *       <ol>
   *         <li>When a thread attaches a listener to a {@code ListenableFuture} that's already
   *             complete, the listener runs immediately in that thread.
   *         <li>When a thread attaches a listener to a {@code ListenableFuture} that's
   *             incomplete and the {@code ListenableFuture} later completes normally, the
   *             listener runs in the thread that completes the {@code ListenableFuture}.

      }
    }

    void stopInterrupting() {
      shouldStop = true;
    }
  }

  /** Interrupts the current thread after sleeping for the specified delay. */
  static void requestInterruptIn(long time, TimeUnit unit) {
    checkNotNull(unit);
    Thread interruptee = Thread.currentThread();
    new Thread(
            new Runnable() {
              @Override
              public void run() {
                try {

    @Override
    public boolean offer(E o) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.offer(o);
    }

    @Override
    public @Nullable E poll() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.poll();
    }

    @Override
    public E remove() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.remove();
    }

    @Override

        return instance;
    }

    /**
     * Starts the process.
     */
    public synchronized void start() {
        if (thread == null) {
            thread = new Thread(this, "CoreLib-TimeoutManager");
            thread.setDaemon(true);
            thread.start();
            if (logger.isDebugEnabled()) {
                logger.debug("TimeoutManager started.");
            }
        }
    }

        // start
        AccessTimeoutTarget accessTimeoutTarget = null;
        TimeoutTask accessTimeoutTask = null;
        if (accessTimeout != null) {
            accessTimeoutTarget = new AccessTimeoutTarget(Thread.currentThread());
            accessTimeoutTask = TimeoutManager.getInstance().addTimeoutTarget(accessTimeoutTarget, accessTimeout, false);
        }

        try {

    }
  }

  /** Wait for the given thread to reach the {@link State#TIMED_WAITING} thread state. */
  @SuppressWarnings("ThreadPriorityCheck") // TODO: b/175898629 - Consider onSpinWait.
  void awaitTimedWaiting(Thread thread) {
    while (true) {
      switch (thread.getState()) {
        case BLOCKED:
        case NEW:
        case RUNNABLE:
        case WAITING:
          Thread.yield();
          break;

            coordinatorWaiting = false
          }
        }
      }
    }
  }

  /** Start another thread, unless a new thread is already scheduled to start. */
  private fun startAnotherThread() {
    assertLockHeld()
    if (executeCallCount > runCallCount) return // A thread is still starting.

    executeCallCount++
    backend.execute(this@TaskRunner, runnable)
  }