Examine source code of Firefox ball

{
  "theme": {
    "images": {
      "theme_frame": "firefoxbolle.jpg"
    },
    "colors": {
      "frame": "#00ffaa",
      "tab_background_text": "#00ffaa"
    }
  },
  "version": "2.0",
  "name": "Firefox ball",
  "manifest_version": 2
}