Examine source code of Tab Close Button

{
  "description": "Adds a button to the address bar that closes the current tab.",
  "manifest_version": 2,
  "name": "Tab Close Button",
  "version": "1.5resigned1",
  "homepage_url": "https://github.com/moben/tab-close-webext",
  "icons": {
    "96": "icons/ic_menu_stop.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "page_action": {
    "default_icon": "icons/ic_menu_stop.png",
    "default_title": "Close this tab",
    "browser_style": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ab300b16-85cb-4380-bdb8-fa96903f2b3c}"
    }
  }
}