Examine source code of Responsive Viewer GT

{
  "manifest_version": 2,
  "name": "Responsive Viewer",
  "version": "1.3",
  "description": "View and test websites in different screen resolutions and devices for responsive design.",
  "permissions": [
    "tabs",
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "32": "icons/logo_32.png",
      "64": "icons/logo_64.png",
      "128": "icons/logo_128.png"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{5452383b-2603-4d0e-b094-b377546badad}"
    }
  }
}