Fresh off its debut at Mobile World Congress in Barcelona, Mozilla’s mobile FirefoxOS now has perhaps its biggest early adopter: Twitter. Engineer Manuel Deschamps says Twitter for FirefoxOS will be available in the app store from the first day the devices begin to ship. The app mirrors the layout on other mobile operating systems, with the same Home, Connect, Discover, and me tabs. It will also support Firefox’s unique Web Activities feature, which will allow users to tweet a photo from any app that also suports Web Activities, which includes the built-in photos app.