Follow-up to #1510544: Allow to preview content in an actual live environment
Problem/Motivation
The 'theming' styling for the node preview bar is within Bartik's style.css. This includes the background colour. If the user is using a theme that is not Bartik then there is no background styles and it's hard to read the UI elements within the bar.
This feel inconsistent with the toolbar, which has it's own styling regardless of theme.
Proposed resolution
Move the styling in the node modules node.preview.css file.
Remaining tasks
User interface changes
A useable node preview bar in all themes
API changes
None