code: public UI wrapLayout(Layout layout) {
          // TODO: add a header to switch the style, etc
          // TODO: add bookmark to set the style
          if (server.getConfig().isDevelopmentHeader()) {
              final VerticalSplitPanel mainLayout = new VerticalSplitPanel();
              mainLayout.setSizeFull();
              mainLayout.setSplitPosition(SPLIT_POSITION, Sizeable.Unit.PIXELS);
              mainLayout.setLocked(true);
  
              final DevApplicationHeader header = new DevApplicationHeader(server);
              header.setSpacing(true);
              mainLayout.setFirstComponent(header);
  
              mainLayout.setSecondComponent(layout);
  
              return new DevUI(mainLayout);
          } else {
              return new DevUI(layout);
          }
      }
docs: Wraps a {@link Layout} into a Vaadin application.
  
  @param layout the layout to wrap
  @return an application displaying that layout