Examine source code of Double-click Tab Closer

{
  "manifest_version": 2,
  "name": "Double-click Tab Closer",
  "version": "1.0",
  "description": "Close the current tab by double-clicking the tab instead of clicking the 'x' button.",
  "permissions": [
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c8a9345e-a66b-486c-8bf2-815e47d1f02f}"
    }
  }
}