Examine source code of Dead Bird

{
  "theme": {
    "images": {
      "theme_frame": "deadbird.jpg"
    },
    "colors": {
      "frame": "#4f4f4f",
      "tab_background_text": "#66ff99"
    }
  },
  "version": "2.0",
  "name": "Dead Bird",
  "manifest_version": 2,
  "description": "Dead Bird is almost invisible against the rocks."
}