Examine source code of Clock-hours

{
  "manifest_version": 2,
  "name": "Clock-hours",
  "version": "1.0",
  "description": "Adds hour part of clock in Toolbar",
  "icons": {
    "48": "icon48.png"
  },
  "browser_action": {
    "default_icon": "none.png",
    "default_title": "clock-hours"
  },
  "background": {
    "scripts": [
      "badge-clock.js"
    ]
  }
}