Examine source code of Firefox - eye animation

{
  "theme": {
    "images": {
      "theme_frame": "foxeyeanimation.png"
    },
    "colors": {
      "frame": "#f5d142",
      "tab_background_text": "#292929"
    }
  },
  "version": "2.0",
  "name": "Firefox - eye  animation",
  "manifest_version": 2,
  "description": "animated, little background "
}