Function execute

test/common/wpt.js:540–554

(fn)

  const queue = [];

  const execute = async (fn) => {
    if (running < concurrency) {
      running++;
      try {
        await fn();
      } finally {
        running--;
        if (queue.length > 0) {
          execute(queue.shift());
        }
      }
    } else {
      queue.push(fn);
    }
  };

  return execute;
};