_fixImageCoordinates(imageToCache) {
    if (imageToCache.width === 0) {
      document.body.appendChild(imageToCache);
      imageToCache.width = imageToCache.offsetWidth;
      imageToCache.height = imageToCache.offsetHeight;
      document.body.removeChild(imageToCache);
    }
  }
IE11 fix -- thanks dponch!

Local helper function
@param {vis.Image} imageToCache
@private