Examine source code of Clear Page Zoom

{
  "manifest_version": 2,
  "name": "Clear Page Zoom",
  "version": "1.0",
  "description": "Quickly resets the zoom level of the current page to default (100%).",
  "permissions": [
    "tabs",
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "Reset Zoom"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{bd379953-e276-4140-867b-5c0801621d04}"
    }
  }
}