Examine source code of Clock: Minutes

{
  "manifest_version": 2,
  "name": "Clock: Minutes",
  "version": "1.1",
  "description": "Adds minutes part of clock in Toolbar",
  "icons": {
    "48": "icon48.png",
    "96": "icon96.png"
  },
  "browser_action": {
    "default_icon": "none.png",
    "default_title": "Minutes"
  },
  "background": {
    "scripts": [
      "badge-clock.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{6c062a8e-82c7-43cc-9f7b-c115356e7c51}"
    }
  }
}