Examine source code of HarlemShake

{
  "manifest_version": 2,
  "name": "HarlemShake",
  "version": "1.3resigned1",
  "description": "Makes website to do a Harlem Shake.",
  "icons": {
    "48": "icons/hs48.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icons/hs.png",
    "default_title": "HarlemShake"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{3a941747-4525-47b8-8c0c-a980023208bb}"
    }
  }
}