Examine source code of Dark knight

{
  "theme": {
    "images": {
      "theme_frame": "darkknight.jpg"
    },
    "colors": {
      "frame": "#000000",
      "tab_background_text": "#f7f2f2"
    }
  },
  "version": "2.0",
  "name": "Dark knight",
  "manifest_version": 2
}