Examine source code of Audio Bluetooth Sync

{
  "manifest_version": 2,
  "name": "Audio Bluetooth Sync",
  "version": "1.4",
  "description": "Adjustable video delay for syncing with Bluetooth audio",
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "permissions": [
    "<all_urls>",
    "storage"
  ],
  "web_accessible_resources": [
    "injected.js"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start",
      "all_frames": true,
      "match_about_blank": true
    }
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Audio Delay Settings",
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "audio-bluetooth-sync@example.org",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}