Examine source code of MozSteamFirefox

{
  "theme": {
    "images": {
      "theme_frame": "pers_head_ff.png"
    },
    "colors": {
      "frame": "#383633",
      "tab_background_text": "#d4cfcc"
    }
  },
  "version": "2.0",
  "name": "MozSteamFirefox",
  "manifest_version": 2,
  "description": "MozSteam with integrated Firefox Logo"
}