Examine source code of Close This Tab

{
  "manifest_version": 2,
  "name": "Close This Tab",
  "version": "1.2",
  "description": "Adds a border to the bottom left and right hand side of all pages that when clicked closes the tab.",
  "icons": {
    "48": "icons/border-48.png"
  },
  "permissions": [
    "<all_urls>",
    "tabs"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "borderify.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "bg.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{cfd55152-c7e8-4ee2-8072-ea86af81d5d7}"
    }
  }
}