message: Restore the tab spacing setting in the Ace text viewer.
diff: @@ -336,14 +336,11 @@ export class TextViewer extends ViewerElement implements Commandable, AcceptsKey
  }
  getTabSize(): number {
  -// FIXME
  - // return parseInt(this._codeMirror.getOption("tabSize"), 10);
  - return 4;
  + return this._aceEditSession.getTabSize();
  }
  setTabSize(size: number): void {
  -// FIXME
  - // this._codeMirror.setOption("tabSize", size);
  + this._aceEditSession.setTabSize(size);
  }
  getBulkFileHandle(): BulkFileHandle {
  