Examine source code of HidePass

{
  "manifest_version": 2,
  "name": "HidePass",
  "version": "1.0.4resigned1",
  "description": "Completely hides all typed passwords in password fields- even asterisks- so that the length of your password cannot be determined.",
  "applications": {
    "gecko": {
      "id": "rosshill@protonmail.com",
      "strict_min_version": "42.0"
    }
  },
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "hidepass.js"
      ]
    }
  ]
}