idle2 should now run.
      tr.b.forcePendingRAFTasksToRun(0);
      assert.isFalse(idle1Ran);
      assert.isTrue(idle2Ran);
    });
  });

  function withFixedIdleTimeRemaining(idleTime, func) {
    const oldRIC = window.requestIdleCallback;
    try {
      const pendingIdleCallbacks = [];
      window.requestIdleCallback = function(callback) {
        const deadline = {
          timeRemaining() {
            return idleTime;
          }
        };
        pendingIdleCallbacks.push(function() {
         