Examine source code of Speedtest button

{
  "manifest_version": 2,
  "name": "Speedtest button",
  "version": "1.0",
  "description": "Speedtest button opens in a tab",
  "background": {
    "scripts": [
      "button.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "48": "icon.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{85152ce5-f302-4c16-b81d-99ba9a5fee3f}"
    }
  }
}