Examine source code of MaxLength Revealer

{
  "manifest_version": 2,
  "name": "MaxLength Revealer",
  "version": "1.1",
  "description": "Displays the maximum length of the password field. Useful for people who use password managers and have long, random passwords.",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "reveal.js"
      ],
      "all_frames": true
    }
  ]
}