Examine source code of Tab Tracker

{
  "manifest_version": 2,
  "name": "Tab Tracker",
  "version": "1.0",
  "description": "Track time spent on each tab",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "permissions": [
    "tabs",
    "storage"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{6064019a-f3cf-4f05-86a3-eaa62c0b82b0}"
    }
  }
}