Examine source code of passview

{
  "manifest_version": 2,
  "name": "passview",
  "version": "1.0",
  "description": "Show the password while hovering on it.",
  "icons": {
    "48": "icons/eye.png"
  },
  "background": {
    "scripts": [
      "passview.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{26b30f1e-9b0e-4b0e-9849-b6dad755586d}"
    }
  }
}