Examine source code of Brushed Firefox

{
  "theme": {
    "images": {
      "theme_frame": "Brushed_Firefox_1.jpg"
    },
    "colors": {
      "frame": "#cccccc",
      "tab_background_text": "#666666"
    }
  },
  "version": "2.0",
  "name": "Brushed Firefox",
  "manifest_version": 2,
  "description": "A simple brushed aluminium effect background with the original Firefox logo."
}