Examine source code of File System Access

{
  "description": "The File System Access API allows web apps to interact with files on the local device.",
  "manifest_version": 2,
  "name": "File System Access",
  "icons": {
    "32": "/icon.png"
  },
  "version": "0.9.4",
  "permissions": [
    "nativeMessaging",
    "storage",
    "webNavigation",
    "<all_urls>"
  ],
  "content_scripts": [],
  "background": {
    "scripts": [
      "/lib/enum.js",
      "/lib/util.js",
      "/background/api/fs.js",
      "/background/api/tab.js",
      "/background/main.js"
    ]
  },
  "page_action": {
    "default_popup": "/view/popup.html",
    "browser_style": true,
    "default_icon": {
      "32": "/icon.png"
    }
  },
  "options_ui": {
    "open_in_tab": true,
    "page": "/view/options.html"
  },
  "web_accessible_resources": [
    "*"
  ],
  "externally_connectable": {
    "ids": [
      "*"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "file@example.com"
    }
  }
}