Examine source code of Grey Shape

{
  "theme": {
    "images": {
      "theme_frame": "SimpleGradientTop.png"
    },
    "colors": {
      "frame": "#c4c4c4",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Grey Shape",
  "manifest_version": 2,
  "description": "Simple Gradient for a clear shape of Mozilla Firefox"
}