Examine source code of SF Sunset

{
  "theme": {
    "images": {
      "theme_frame": "ffpbaysunsett.jpg"
    },
    "colors": {
      "frame": "#050000",
      "tab_background_text": "#e6f5f7"
    }
  },
  "version": "2.0",
  "name": "SF Sunset",
  "manifest_version": 2,
  "description": "San Francisco sunset seen from the Oakland Hills."
}