**Feature Request** #### What is the expected behavior? Specify custom CSS classes for overlay backdrops for certain dialogs. #### What is the current behavior? Backdrops can not be individually styled. If I wanted to remove or style a backdrop it would have to be styled for all backdrops on all dialogs. #### What is the use-case or motivation for changing an existing behavior? To remove/style backdrops for specific dialogs. One dialog may not need a backdrop, or a backdrop with a different color or opacity.