function CanvasTileLayer(canvas_setup, render) {
  this.tileSize = new google.maps.Size(256, 256);
  this.maxZoom = 19;
  this.name = "Tile #s";
  this.alt = "Canvas tile layer";
  this.tiles = {};
  this.canvas_setup = canvas_setup;
  this.render = render;
  if (!render) {
      this.render = canvas_setup;
  }
}
Schedule a requestAnimationFrame callback to updateHandler. If one is
already scheduled, there is no effect.