Examine source code of Tab Origin

{
  "manifest_version": 2,
  "name": "Tab Origin",
  "description": "Return to the page from which you opened this tab.",
  "author": "Peter Elmers",
  "version": "2.0.1resigned1",
  "icons": {
    "48": "drawing.png",
    "128": "drawing128.png"
  },
  "permissions": [
    "tabs",
    "storage"
  ],
  "browser_action": {
    "default_icon": "drawing.png"
  },
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "default": "Ctrl+Shift+U"
      }
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "jid1-x6Qlg0BY3jAeaQ@jetpack"
    }
  }
}