Examine source code of Trim Scroll

{
  "manifest_version": 2,
  "name": "Trim Scroll",
  "description": "alternative scroll in large page",
  "version": "1.1",
  "default_locale": "en",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "menus",
    "activeTab",
    "storage"
  ],
  "options_ui": {
    "page": "options.html"
  },
  "icons": {
    "16": "icons/trim_scroll_16.png",
    "32": "icons/trim_scroll_32.png",
    "48": "icons/trim_scroll_48.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e324b516-f4f4-41c9-98a3-be47c77179df}"
    }
  }
}