Examine source code of Firefox Trees 2017

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "rgba(229,230,232,1)",
      "tab_background_text": "#000"
    }
  },
  "version": "2.0",
  "name": "Firefox Trees 2017",
  "manifest_version": 2,
  "description": "Based on the Mozilla Firefox website splash screen. Image copyright of Mozilla Firefox at <a rel=\"nofollow\" href=\"https://outgoing.prod.mozaws.net/v1/bda24eba4e3eeb6e74946dcfcc4ad7ae8b87e192e8266cf75786441d8a3b31e8/http%3A//www.firefox.com\">www.firefox.com</a>."
}