Examine source code of Auto Password Mask

{
  "manifest_version": 2,
  "name": "Auto Password Mask",
  "version": "1.0",
  "description": "Automatically masks any visible passwords in form fields.",
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "mask.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{9ed5208c-0459-48b1-9889-358a7d786b65}"
    }
  }
}