Examine source code of Audible Control

{
  "manifest_version": 2,
  "name": "Audible Control",
  "version": "0.2resigned1",
  "description": "Control the playback speed of your favorite audiobook on audible. Control from 0.5x to 2.5x. Compatible with most audible sites.",
  "icons": {
    "16": "16.png",
    "48": "48.png",
    "128": "128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.audible.co.uk/cloudplayer*",
        "*://*.audible.com/cloudplayer*",
        "*://*.audible.ca/cloudplayer*",
        "*://*.audible.com.au/cloudplayer*",
        "*://*.audible.co.jp/cloudplayer*",
        "*://*.audible.fr/cloudplayer*",
        "*://*.audible.de/cloudplayer*"
      ],
      "js": [
        "audible_playbackrate.js"
      ],
      "run_at": "document_end",
      "all_frames": true
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{24fa023b-c265-4f33-8ed3-845546f616ad}"
    }
  }
}