1505096 - Update dev tools theme to inherit from Firefox theme when using built in themes

Status: RESOLVED DUPLICATE of bug 1505090

(DevTools :: General, enhancement)

Description

[Asif Youssuff]

Spawned from discussion in bug 1471163

> I started by updating my Firefox theme to the dark theme, and was surprised when it didn't update dev tools. I wondered why the Firefox theme didn't simply apply to the dev tools theme.

In the default state for stable and developer edition, Firefox arrives with theme defaults of "Light", "Dark" and Default. 

Right now, there is no relationship between the Firefox theme and the dev tools theme; updating the Firefox theme does not change the Firefox dev tools UI.

Ideally, updating the selecting either "default" or "light" in the Firefox customize UI would also update the theme in dev tools.

In order to continue to allow users to have a different theme in dev tools vs. Firefox, a new (default) option could be added to the dev tools settings UI - in addition to "Dark" and "Light", "Default" could be added, which would inherit the theme preference from Firefox's customize UI.

Users could then override the preference in dev tools settings to either "Dark" or "Light". 

Proposed mapping for default themes:

Firefox Default :: Dev tools "Light"
Firefox Light :: Dev tools "Light"
Firefox Dark :: Dev tools "Dark"

These would all appear as "Default" in the dev tools settings UI, but allowing an override via the existing checkbox.