Examine source code of Firefox Eye

{
  "theme": {
    "images": {
      "theme_frame": "persona_3_head.png"
    },
    "colors": {
      "frame": "#bfbfbf",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "Firefox Eye",
  "manifest_version": 2,
  "description": "Eye with build in firefox-logo"
}