Examine source code of Visit Counter

{
  "manifest_version": 2,
  "name": "Visit Counter",
  "version": "26.3.14",
  "description": "Adds toolbar button that shows the number of visits made to the current URL",
  "author": "Aezay",
  "permissions": [
    "history",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon-hash.svg"
  },
  "icons": {
    "16": "icon-hash.svg",
    "32": "icon-hash.svg",
    "48": "icon-hash.svg"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "Visit.Counter@Aezay.Addons",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}