Examine source code of Firefox and Circles

{
  "theme": {
    "images": {
      "theme_frame": "firefox-header.png"
    },
    "colors": {
      "frame": "#ffffff",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Firefox and Circles",
  "manifest_version": 2,
  "description": "This is a clean persona, with a blue gradient, yellow circles and an orange Firefox logo."
}