Grid missing scroll bar on firefox with large data sets

[dve]

When using Grid with large datasets (500,000 entries) the scroll bar is not visible on firefox. If the dataset is smaller (50,000 entries) or using chrome everything is fine. Tested with vaadin 8.7.1

Example:

public class GridTest extends UI
{
   public class Bean
   {
      private final int id;

      public Bean(int id)
      {
         super();
         this.id = id;
      }

      public int getId()
      {
         return id;
      }
   }

   @Override
   protected void init(VaadinRequest request)
   {
      Grid<Bean> grid = new Grid<>(Bean.class);
      grid.setDataProvider(new AbstractBackEndDataProvider<Bean, String>()
      {
         @Override
         protected Stream<Bean> fetchFromBackEnd(Query<Bean, String> query)
         {
            List<Bean> beans = new ArrayList<>();
            for (int i = query.getOffset(); i < query.getOffset()
                  + query.getLimit(); i++)
            {
               beans.add(new Bean(i));
            }
            return beans.stream();
         }

         @Override
         protected int sizeInBackEnd(Query<Bean, String> query)
         {
            return 520000;
         }
      });
      setContent(grid);
   }
}

[Legioth]

Most likely a variation of #9752.