Examine source code of Coursera Playback Speed

{
  "description": "Allows you to set playback speed to any value (from 0.25x to 10x)",
  "manifest_version": 2,
  "name": "Coursera Playback Speed",
  "short_name": "Coursera Playspeed",
  "version": "1.1",
  "icons": {
    "48": "icon48.png",
    "96": "icon96.png",
    "128": "icon128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.coursera.org/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "hook.js"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{7057f4e5-f4db-44f3-954f-6ea74951bebb}"
    }
  }
}