function updateUntilDone(globe, scene) {
      // update until the load queue is empty.
      return pollToPromise(function () {
        globe._surface._debug.enableDebugOutput = true;
        scene.render();
        return (
          globe._surface._tileLoadQueueHigh.length === 0 &&
          globe._surface._tileLoadQueueMedium.length === 0 &&
          globe._surface._tileLoadQueueLow.length === 0 &&
          globe._surface._debug.tilesWaitingForChildren === 0
        );
      });
    }
Repeatedly calls update until the load queue is empty.  Returns a promise that resolves
once the load queue is empty.

@param {Ray} ray The ray to test for intersection.
@param {Scene} scene The scene.
@return {Promise<boolean>}

@private