Examine source code of Stopwatch & Timer

{
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "version": "1.0",
  "description": "__MSG_extensionDescription__",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/icon-16.png",
      "48": "icons/icon-48.png",
      "128": "icons/icon-128.png"
    }
  },
  "permissions": [],
  "browser_specific_settings": {
    "gecko": {
      "id": "{2d1a0b86-cd1c-4630-b907-64831bcc71e2}"
    }
  }
}