Examine source code of HappyViewer

{
  "manifest_version": 2,
  "name": "HappyViewer",
  "version": "1.3",
  "icons": {
    "48": "icons/icon-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "happyViewer.js"
      ],
      "css": [
        "hev.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{7038133b-b9de-464c-83ad-11406bf32daf}"
    }
  }
}