Examine source code of UseCached

{
  "description": "switch webpage to google webcache.",
  "manifest_version": 2,
  "name": "UseCached",
  "version": "1.3resigned1",
  "homepage_url": "https://github.com/fatzombi/UseCached",
  "icons": {
    "48": "icons/on.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "page_action": {
    "default_icon": "icons/off.svg",
    "browser_style": true
  },
  "permissions": [
    "http://*/*",
    "https://*/*",
    "activeTab",
    "tabs"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{23d59a8f-40e4-4671-b700-f11008a51ee2}"
    }
  }
}