Examine source code of Accept Language Switcher

{
  "name": "Accept Language Switcher",
  "manifest_version": 2,
  "version": "0.0.2resigned1",
  "icons": {
    "96": "index.png"
  },
  "browser_action": {
    "browser_style": true,
    "default_icon": {
      "19": "index.png",
      "38": "index.png"
    },
    "default_title": "Whereami?",
    "default_popup": "popup/ui.html"
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "storage",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "setAcceptLanguage.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{4ce0486a-8cb4-4887-9174-3f351eeec0c6}"
    }
  }
}