Method _requestFileSizeAsync

src/backend/XmlHttpRequest.ts:434–436

* Only requests the HEAD content, for the file size.

(path: string, cb: BFSCallback<number>)

   * Only requests the HEAD content, for the file size.
   */
  private _requestFileSizeAsync(path: string, cb: BFSCallback<number>): void {
    getFileSizeAsync(this.getXhrPath(path), cb);
  }
  private _requestFileSizeSync(path: string): number {
    return getFileSizeSync(this.getXhrPath(path));
  }