Examine source code of moz://a

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#223a7d",
      "tab_background_text": "#ff681c"
    }
  },
  "version": "2.0",
  "name": "moz://a",
  "manifest_version": 2,
  "description": "moz://a\nmozilla firefox"
}