Examine source code of Thumbnail Downloader

{
  "name": "Download thumbnails",
  "description": "Download thumbnails of a video",
  "update_url": "http://clients2.google.com/service/update2/crx",
  "version": "5.5resigned1",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "name": "Download youtube,vimeo thumbnails",
    "default_popup": "popup.html",
    "default_icon": {
      "16": "1.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.youtube.com/*"
      ],
      "js": [
        "jquery.js",
        "download.js"
      ],
      "run_at": "document_end"
    }
  ],
  "icons": {
    "16": "1.png",
    "48": "2.png",
    "128": "3.png"
  },
  "web_accessible_resources": [
    "*.png",
    "*.PNG"
  ],
  "permissions": [
    "tabs",
    "*://*.youtube.com/*",
    "*://*.vimeo.com/*"
  ],
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "{80c95a34-36dd-4482-ac2f-b6ef315ea9cb}"
    }
  }
}