Examine source code of Cool clock

{
  "manifest_version": 2,
  "name": "Cool clock",
  "version": "1.0",
  "permissions": [
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Cool clock",
    "default_icon": {
      "16": "icons/icon.png",
      "32": "icons/icon.png",
      "64": "icons/icon.png"
    }
  },
  "web_accessible_resources": [
    "hello.html"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{095a7299-3170-425b-b32b-6b01699d23dc}"
    }
  }
}