Examine source code of lets flip a coin

{
  "theme": {
    "images": {
      "theme_frame": "X-KH-gimplogofirefox.8.1.jpg"
    },
    "colors": {
      "frame": "#f7ff00",
      "tab_background_text": "#bbff00"
    }
  },
  "version": "2.0",
  "name": "lets flip a coin",
  "manifest_version": 2,
  "description": "...ya let´s do that"
}