Examine source code of plexiglass

{
  "manifest_version": 2,
  "name": "Plexiglass",
  "version": "1.0",
  "description": "Removes mouse cursor and adds black opaque overlay to page.",
  "icons": {
    "32": "icons/plexiglass-32.png",
    "48": "icons/plexiglass-48.png"
  },
  "permissions": [
    "activeTab",
    "cookies",
    "<all_urls>"
  ],
  "browser_action": {
    "default_icon": "icons/plexiglass-32.png",
    "default_title": "Plexiglass Options",
    "default_popup": "popup/glass_options.html"
  }
}