Examine source code of Audio Mirror

{
  "manifest_version": 2,
  "name": "Audio Mirror",
  "version": "1.0",
  "description": "Mirror audio from one tab to another (via MediaStream and iframe).",
  "permissions": [
    "tabs",
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "web_accessible_resources": [
    "mirror.html"
  ],
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ffc21a77-337b-42a7-b38d-34f35b3d5df2}"
    }
  }
}