Examine source code of Simple gradients

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#d6dce1",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "Simple gradients",
  "manifest_version": 2,
  "description": "The aim of the theme is to bring the gradients of Firefox for Windows to Linux distros. See <a rel=\"nofollow\" href=\"https://outgoing.prod.mozaws.net/v1/b82d480f28b2ecef2df25a56758f29478125758c75b36a0dd3ad39795ade0d4c/http%3A//getfirefox.com\">getfirefox.com</a> and have a look at the screenshot: you might be able to see the relation."
}