Examine source code of Webpage Time Tracker

{
  "manifest_version": 2,
  "name": "Webpage Time Tracker",
  "version": "1.4",
  "description": "Keep track of how you spend your time on the web.",
  "icons": {
    "128": "icon_128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "idle",
    "tabs"
  ],
  "browser_action": {
    "default_title": "Webpage Time Tracker",
    "default_icon": "icon_19.png",
    "default_popup": "popup.html"
  },
  "content_security_policy": "script-src 'self' 'unsafe-eval' https://www.gstatic.com; object-src 'self'"
}