Examine source code of List Tabs

{
  "name": "List Tabs",
  "description": "Lists all tabs",
  "manifest_version": 2,
  "version": "2.1.0",
  "icons": {
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "64": "icons/icon-64.png"
  },
  "permissions": [
    "tabs",
    "activeTab",
    "bookmarks"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "32": "icons/icon-32.png"
    }
  },
  "author": "Valentine Rybin",
  "browser_specific_settings": {
    "gecko": {
      "id": "@list_tabs"
    }
  }
}