Examine source code of Green and black gradient

{
  "theme": {
    "images": {
      "theme_frame": "Firefox.jpg"
    },
    "colors": {
      "frame": "#999999",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Green and black gradient",
  "manifest_version": 2,
  "description": "This is just a trial, but you can use it. It's made of brushes from photoshop."
}