Examine source code of Tab Thumbnail Viewer

{
  "manifest_version": 2,
  "name": "Tab Thumbnail Viewer",
  "version": "1.0",
  "description": "Preview and switch tabs with thumbnails.",
  "permissions": [
    "tabs"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "View Tabs"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a2358640-4c6b-4112-813a-2d6d27df4e00}"
    }
  }
}