Examine source code of SpeedX

{
  "manifest_version": 2,
  "name": "SpeedX",
  "version": "1.1",
  "description": "Adjusts video playback speed for Firefox",
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_action": {
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c730f0d2-d397-4ca4-9b0b-7110b94b9d0f}"
    }
  }
}