Examine source code of CloseTabsByDomain

{
  "manifest_version": 2,
  "name": "CloseTabsByDomain",
  "description": "Close all tabs by domain",
  "version": "1.2.0",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "16": "img/logo/icon_16.png",
    "48": "img/logo/icon_48.png",
    "128": "img/logo/icon_128.png"
  },
  "permissions": [
    "tabs",
    "storage",
    "contextMenus"
  ],
  "options_page": "options.html",
  "browser_action": {
    "default_icon": {
      "16": "img/logo/icon_16.png",
      "48": "img/logo/icon_48.png"
    },
    "default_title": "CloseByDomain",
    "default_popup": "popup.html"
  },
  "default_locale": "en",
  "browser_specific_settings": {
    "gecko": {
      "id": "{8f5bd3f8-ade7-490f-a07d-1c3d9ee5096f}"
    }
  }
}