ent RAF task queue.

      let idle1Ran = false;
      let idle2Ran = false;
      tr.b.requestIdleCallback(function() {
        fakeNow += 100;
        idle1Ran = true;
      });
      tr.b.requestIdleCallback(function() {
        fakeNow += 1;
        idle2Ran = true;
      });
      fakeNow = 10000;
      tr.b.forcePendingRAFTasksToRun(0);
      assert.isTrue(idle1Ran);
      assert.isFalse(idle2Ran);

      // Reset idle1Ran to verify that it dosn't run again.
      idle1Ran = false;

      // Now run. 