Currently, our app CSS stylesheets are generated from sources in at least three different places:
1) MobileFrontend;
2) the MobileApp extension; and
3) I believe the iOS app has some .less files living in its repo.
On Android we update our CSS by firing up and updating mw-vagrant and manually running a shell script[1] as often as someone thinks to do it. I'm not sure what the update strategy is for the iOS app. The styles in the MobileApp extension don't get a lot of attention, and we're not really frontend web devs.
I believe it would improve cross-mobile-platform consistency and communication to keep all of our CSS styling code in one place. I propose that that be MobileFrontend, since we're all ultimately dependent on it. I suspect that having the "app-specific" code in the same repo would help the mobile web devs anticipate possible effects of changes on mobile apps and encourage discussion about upcoming changes. Consolidation could also work hand-in-hand with the kind of unit testing that Joaquin mentioned in the recent email thread about the iOS srcset regression.
What do you think?
[1] https://git.wikimedia.org/blob/apps%2Fandroid%2Fwikipedia.git/master/scripts%2Fmake-css-assets.bash