message: Doc some values
diff: @@ -25,10 +25,14 @@ import { EventType, MsgType } from "matrix-js-sdk/src/@types/event";
  // TODO: We should consider caching the blobs. https://github.com/vector-im/element-web/issues/17192
  export class MediaEventHelper implements IDestroyable {
  + // Either an HTTP or Object URL (when encrypted) to the media.
  public readonly sourceUrl: LazyValue<string>;
  public readonly thumbnailUrl: LazyValue<string>;
  +
  + // Either the raw or decrypted (when encrypted) contents of the file.
  public readonly sourceBlob: LazyValue<Blob>;
  public readonly thumbnailBlob: LazyValue<Blob>;
  +
  public readonly media: Media;
  public constructor(private event: MatrixEvent) {
  