code: function() {
          if (!this.imgDiv || this.isLoading) {
              return;
          }
          var backBuffer;
          if (this.frame) {
              backBuffer = this.frame.cloneNode(false);
              backBuffer.appendChild(this.imgDiv);
          } else {
              backBuffer = this.imgDiv;
          }
          this.imgDiv = null;
          return backBuffer;
      }
docs: Method: createBackBuffer
  Create a backbuffer for this tile. A backbuffer isn't exactly a clone
  of the tile's markup, because we want to avoid the reloading of the
  image. So we clone the frame, and steal the image from the tile.
  
  Returns:
  {DOMElement} The markup, or undefined if the tile has no image
  or if it's currently loading.