In Dark Mode, grayed-out menu items look like normal menu items

[t-m-w]

Screenshots:

Light	Dark

The Light screenshot shows grayed-out "Backup now" and "Restore backup" menu items. The Dark screenshot shows "Backup now" and "Restore backup" menu items that are the same color as the others.

The effect is that the user may be confused by nothing happening when they tap one of these items.

May be related to #750

[grote]

@theimpulson I think this is related to your MD3 changes. Do you know how to bring back disabled menu items in dark theme?

[theimpulson]

This should be fixed by dropping the theme attribute from the Toolbar. I have included this in #776 PR but we can move it to a standalone one too if required.

dc0a511