Examine source code of LockMyWeb

{
  "manifest_version": 2,
  "name": "LockMyWeb",
  "version": "1.0",
  "description": "Adds password protection to your browser sessions.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "storage",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a527455d-eddd-402b-aab7-7005f40b6ee3}"
    }
  }
}