message: VideoResource should override source type
diff: @@ -25,6 +25,8 @@ export interface IVideoResourceOptionsElement
  */
  export class VideoResource extends BaseImageResource
  {
  + /** Override the source to be the video element. */
  + public source: HTMLVideoElement;
  protected _autoUpdate: boolean;
  protected _isConnectedToTicker: boolean;
  protected _updateFPS: number;
  