Examine source code of Youtube Speedier

{
  "manifest_version": 2,
  "name": "Youtube Speedier",
  "version": "1.0",
  "description": "Automatically speeds up youtube videos, and lets you tweak playback speed",
  "icons": {
    "48": "icon-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "speedup.js"
      ]
    }
  ]
}