Examine source code of Track Browsing Time

{
  "manifest_version": 2,
  "name": "Track Browsing Time",
  "version": "2.1",
  "description": "Tracks your browsing time on any given domain",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "webNavigation",
    "storage"
  ],
  "browser_action": {
    "default_icon": "icons/icon.png",
    "default_title": "Track Browse Time",
    "default_popup": "view.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{9fce8a1f-e2c4-4010-b174-25ab27f33c3f}"
    }
  }
}