Examine source code of chronos

{
  "manifest_version": 2,
  "name": "chronos",
  "short_name": "chronos",
  "description": "Browser extension for visualizing web browsing activity",
  "version": "1.1.1",
  "icons": {
    "16": "logo16.png",
    "32": "logo32.png",
    "48": "logo48.png",
    "96": "logo96.png",
    "128": "logo128.png"
  },
  "background": {
    "page": "index.html"
  },
  "browser_action": {
    "default_icon": "logo96.png",
    "default_title": "View web browsing activity"
  },
  "content_security_policy": "script-src 'self'; object-src 'self';",
  "permissions": [
    "idle",
    "tabs"
  ]
}