Examine source code of Watch Time

{
  "manifest_version": 2,
  "name": "Watch Time",
  "version": "2.0",
  "description": "Tracks your browsing time on any given domain",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "webNavigation",
    "storage"
  ],
  "browser_action": {
    "default_icon": "icon128-2.png",
    "default_title": "Browse Time",
    "default_popup": "view.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{78c856d1-898f-4586-bc02-4725f9235a9d}"
    }
  }
}