Examine source code of Meetrics OptOut

{
  "name": "Meetrics-Unmeasurable",
  "version": "1.1resigned1",
  "manifest_version": 2,
  "description": "Blocks requests from Meetrics to prevent tracking",
  "icons": {
    "48": "Icon_48x48.png"
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "unread.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{1255a0a0-9c4a-4333-a8fe-249fdb860c38}"
    }
  }
}