Examine source code of about:newTab simple Clock

{
  "description": "Adds simple Clock on your about:newtab",
  "manifest_version": 2,
  "name": "newTabTime",
  "version": "2.3.6",
  "chrome_url_overrides": {
    "newtab": "index.html"
  },
  "icons": {
    "48": "icons/newTabTime-48.png"
  },
  "browser_action": {
    "browser_style": true,
    "default_popup": "settings/options-popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png",
      "64": "icons/icon64.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{99c26658-c46a-4f57-a056-b4259e589729}",
      "strict_min_version": "100.0"
    }
  },
  "options_ui": {
    "page": "settings/options.html",
    "open_in_tab": true,
    "browser_style": true
  },
  "permissions": [
    "storage"
  ]
}