Examine source code of Web Time Tracker1

{
  "manifest_version": 2,
  "name": "Web Time Tracker",
  "version": "1.0",
  "description": "Track time spent on each website daily.",
  "permissions": [
    "tabs",
    "storage",
    "webNavigation"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Web Time Tracker"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{2a6cc07d-ce81-4be5-953e-a87596e73d88}"
    }
  }
}