Examine source code of Auto Cookie Injector

{
  "manifest_version": 2,
  "name": "Auto Cookie Injector",
  "version": "1.2",
  "description": "Injects specific cookies and user-agent on all websites with options.",
  "permissions": [
    "cookies",
    "<all_urls>",
    "webRequest",
    "webRequestBlocking",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "16": "icon.png"
    },
    "default_title": "Toggle Cookie Injector",
    "default_popup": "popup.html"
  },
  "applications": {
    "gecko": {
      "id": "autocookieinjector@yourdomain.com"
    }
  }
}