Examine source code of Bring Twitter Bird Back

{
  "manifest_version": 2,
  "name": "BringTwitterBirdBack",
  "version": "1.0",
  "description": "Brings back the Twitter bird icon",
  "icons": {
    "48": "larry.svg"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "index.html",
    "default_icon": {
      "48": "larry.svg"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://twitter.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_end"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{73421972-8878-46da-9802-86d68fc2e6dc}"
    }
  }
}