Examine source code of Unicorn New Tab

{
  "manifest_version": 2,
  "name": "Unicorn New Tab",
  "short_name": "Unicorn",
  "description": "Replace the new tab with a random unicorn or rainbow",
  "version": "2.5.2resigned1",
  "permissions": [
    "tabs",
    "storage",
    "webNavigation",
    "*://*.google.com/*",
    "*://*.github.com/*",
    "*://*.github.io/*",
    "*://*.cloudfare.com/*",
    "*://*.googleapis.com/*",
    "*://*.cornify.com/*",
    "*://*.unsplash.com/*",
    "cookies",
    "<all_urls>"
  ],
  "icons": {
    "19": "icon.png"
  },
  "sandbox": {
    "pages": [
      "unicorn.html"
    ]
  },
  "chrome_url_overrides": {
    "newtab": "unicorn.html"
  },
  "browser_action": {
    "default_title": "Unicorn",
    "default_icon": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{bc0fb197-c7ac-43e6-9b08-0adbf7b7f4b9}"
    }
  }
}