System Information
Operating system: Windows 10
Graphics card: Nvidia Geforce 1080

Blender Version
Broken:
-Date: 2018-11-29 15:57
-Hash: 26d5a3625ed
-Branch: blender2.8
Worked: -

Short description of error

In the 3D viewport, upper right corner has options for different shading styles. From left to right, there's wireframe, solid, lookdev and rendered. Solid shading has a dropdown menu with the options for flat, studio and matcap shading. The studio lighting mode doesn't show any previews of different lighting conditions (I googled online and some earlier posts in the summer revealed that this wasn't always the case. Before, you could set a camera HDRI in the preferences and see it as an option in the lighting: studio -settings in the dropdown menu for the solid shading mode.)

Exact steps for others to reproduce the error
Based on the default startup or an attached .blend file (as simple as possible).

Default startup file.
-Go to the topright corner of the viewport, above the gizmos. Select solid shading mode.
-Open the dropdown menu "Shading".
-The first option, "lighting", doesn't have any thumbnails/previews/options for studio lighting. Flat and Matcap options work just as intended.
-This happens whether I've added a custom camera HDRI or not.
I think the link below shows how it's supposed to work, but I can't get a selection of different studio lighting conditions.
https://blenderartists.org/uploads/default/optimized/4X/3/b/b/3bb63497d20503afe2a064aee260aa8f9ce4cf53_1_433x500.jpg
Here's the full thread.
https://blenderartists.org/t/differece-between-blender-2-8s-camera-and-world-hdri/1117783/6

-Ilari Männistö