Examine source code of Smart Start page

{
  "applications": {
    "gecko": {
      "strict_min_version": "57.0",
      "id": "{e032c490-efd6-41cb-8ec0-421d62d61ca2}"
    }
  },
  "manifest_version": 2,
  "version": "0.4resigned1",
  "name": "Smart Start page",
  "description": "Forms recommendations on the start page based on your preferences.",
  "chrome_settings_overrides": {
    "homepage": "index.html"
  },
  "chrome_url_overrides": {
    "newtab": "index.html"
  },
  "permissions": [
    "history",
    "<all_urls>"
  ]
}