Examine source code of Tool Bar Clock

{
  "manifest_version": 2,
  "name": "Tool Bar Clock",
  "version": "1.0",
  "description": "Display a clock on the toolbar.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "storage",
    "alarms"
  ],
  "browser_action": {
    "default_title": "Tool Bar Clock",
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "applications": {
    "gecko": {
      "id": "tool-bar-clock@example.com"
    }
  }
}