Examine source code of Hide WP admin bar

{
  "description": "Toggle WP admin bar.",
  "manifest_version": 2,
  "name": "Hide WP admin bar",
  "version": "1.3.5",
  "permissions": [
    "https://*/*",
    "http://*/*",
    "tabs"
  ],
  "browser_action": {
    "default_icon": "close-32.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{91c0deb3-aed5-4cdd-bf7d-0cb5d8fe70f3}"
    }
  }
}