Enable using different themes for Firefox and Firefox Nightly

[Flemming]

I am using both the standard Firefox and Firefox Nightly, and I would prefer to make it easy to know which version I am currently using by having different themes active.

When I switch the theme on one of them, the other changes also to use the same theme. So I can not easily distinguish which version I'm using without reading the name in the top left corner.

[jscher2000]

It would be nice to have this setting available on the Add-ons page, Themes panel, or on the Settings page, Sync panel. Then you would not need to discover the following very arcane setting.

There is an undocumented method to modify various details of what Firefox transmits through Sync between your different installations. Although the following change is not officially supported -- because it may break in a future update -- for now, this is how you would do it:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.

(2) In the search box in the page, type or paste activeThemeID and pause while the list is filtered

Firefox should display two preferences: one is the ID itself, and the other is the preference controlling whether to sync that ID.

(3) Double-click the services.sync.prefs.sync.extensions.activeThemeID preference to switch the value from true to false

Also, perhaps this setting should have a default value of false in the first place??