;
    });
    let idleRan = false;
    tr.b.requestIdleCallback(function() {
      idleRan = true;
    });
    tr.b.forcePendingRAFTasksToRun();
    assert.isTrue(rafRan);
    assert.isFalse(idleRan);
  });

  let fakeNow = undefined;
  function withFakeWindowPerformanceNow(func) {
    const oldNow = window.performance.now;
    try {
      window.performance.now = function() { return fakeNow; };
      func();
    } finally {
      window.performance.now = oldNow;
    }
  }

  // None of the following tests 