Examine source code of Tab Capture Sample

{
  "name": "Tab Capture Sample",
  "description": "Capture tab example and play in a <video> element in a second tab.",
  "version": "3.2",
  "manifest_version": 2,
  "background": {
    "scripts": [
      "eventPage.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_icon": "icon.png"
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": false
  },
  "permissions": [
    "storage",
    "tabs",
    "tabCapture"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{e39afda2-1630-4371-931b-7f6ad74e4979}"
    }
  }
}