Examine source code of Audio Panner

{
  "manifest_version": 2,
  "name": "Audio Panner",
  "version": "1.2",
  "description": "Pan audio on the current tab",
  "permissions": [
    "activeTab",
    "tabs",
    "<all_urls>"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icon16.png",
      "32": "icon32.png",
      "48": "icon48.png",
      "64": "icon64.png",
      "128": "icon128.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{3a313322-8d82-47c4-bcce-ef660aedb502}"
    }
  }
}