Examine source code of Remote Control

{
  "manifest_version": 2,
  "name": "Remote Control",
  "version": "1.1.1",
  "description": "Provides default behavior for media players",
  "icons": {},
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "remote_control.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{992ffd41-bae2-480e-9a78-9a4e5f86a6bb}"
    }
  }
}