Major Description
The Spark UI was updated to Bootstrap 4, and during the update the progress bar in the UI was updated to highlight the whole bar once any tasks were in progress, versus highlighting just the number of tasks that were in progress. The was a great visual queue of seeing what percentage of the stage/job was currently being worked on, and it'd be great to get that functionality back.
The change can be found here: https://github.com/apache/spark/pull/27370/files#diff-809c93c57cc59e5fe3c3eb54a24aa96a38147d02323f3e690ae6b5309a3284d2L448
