Examine source code of HTTPS Percentage

{
  "manifest_version": 2,
  "name": "HTTPS Percentage",
  "version": "2.1resigned1",
  "description": "Displays the percentage of network requests that use HTTPS while you browse the Web.",
  "applications": {
    "gecko": {
      "id": "https-percentage@kflag.net",
      "strict_min_version": "59.0"
    }
  },
  "permissions": [
    "<all_urls>",
    "webRequest",
    "idle",
    "storage"
  ],
  "icons": {
    "32": "icons/https-percentage-32.png",
    "48": "icons/https-percentage-48.png"
  },
  "background": {
    "scripts": [
      "browser-polyfill.js",
      "https-percentage.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/https-percentage-32.png",
    "default_title": "HTTPS Percentage",
    "default_popup": "popup/popup.html",
    "browser_style": false
  }
}