Examine source code of Music Progress Bar

{
  "manifest_version": 2,
  "name": "Music Progress Bar",
  "version": "1.0",
  "description": "Thanh tải trang trở thành melody bar: khi % tăng, phát nốt theo thang âm.",
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{489037b7-39b8-4da2-b9ec-2682ab2e0bad}"
    }
  }
}