Examine source code of Page Performance Test

{
  "manifest_version": 2,
  "name": "Window Performance Test",
  "short_name": "Window Performance speed test",
  "description": "Get accurate performance timing for any page with this extension",
  "version": "3.0.2",
  "applications": {
    "gecko": {
      "id": "jid1-6ErcSqy4bjBcBw@jetpack",
      "strict_min_version": "55.0"
    }
  },
  "icons": {
    "16": "assets/icon_16.png",
    "128": "assets/icon_128.png"
  },
  "permissions": [
    "<all_urls>",
    "tabs",
    "*://*/*",
    "http://*/*",
    "https://*/*"
  ],
  "browser_action": {
    "default_icon": "assets/icon_16.png",
    "default_popup": "webperf/popup.html"
  },
  "devtools_page": "devpanel.html",
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}