Examine source code of Share Tab

{
  "manifest_version": 2,
  "name": "Share Tab",
  "version": "0.0.1",
  "description": "Share tabs between computers",
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "32": "share_32.png"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "permissions": [
    "storage",
    "tabs",
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{5f6b6226-ff57-4e45-aa6d-cc28aba3d4cd}"
    }
  }
}