Examine source code of Pop-up Calculator

{
  "manifest_version": 2,
  "name": "Calculator",
  "version": "2.0",
  "description": "Causes a simple calculator to popup in the corner",
  "icons": {
    "48": "icons/calc_icon48.png",
    "96": "icons/calc_icon96.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icons/calc_icon32.png",
    "default_title": "Calculator",
    "default_popup": "popup/calculator.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "calculator@stereng"
    }
  }
}