In a dark theme, the menu bar, title bar and pop-up menus are displayed with a white background

### Expected
When the dark theme is on, the menu bar, title bar and pop-up menus when clicking on File, Edit, etc. on the menu bar are displayed with a dark background.

### Observed
When the dark theme is on, the menu bar, title bar and pop-up menus when clicking on File, Edit, etc. on the menu bar are displayed with a white background.

### Reproduced
1. Click on File in the menu bar
2. Click on Preferences...
3. Click Display
4. Go to Theme
5. Click on Dark
6. Click on File in the menu bar


Make|Model|OS Version|App Version
-|-|-|-
SYSTEM_MAKE|SYSTEM_MODEL|Windows 10 v. 1909|1.12.0

This is due to problem https://github.com/Automattic/simplenote-electron/issues/1036, but I'm also talking about a pop-up window, and it has been a year already, and in applications such as Spotify, Discord, GitHub Desktop, Visual Studio Code, the menu bar, title bar and pop-up windows are dark.

Start by reproducing the issue on Windows 10 through Preferences > Display > Theme, then inspect the Electron menu, title-bar, and pop-up window theme handling. Done means the menu bar, title bar, and File/Edit pop-up menus use dark backgrounds when the Dark theme is selected, without regressing the light theme.

Written by the indexing model from the issue text.