function componentWillReceiveProps(nextProps) {
  console.log("start");
  const { selectedSource } = nextProps;

  if (
    nextProps.startPanelSize !== this.props.startPanelSize ||
    nextProps.endPanelSize !== this.props.endPanelSize
  ) {
    this.state.editor.codeMirror.setSize();
  }
  console.log("done");
}