Examine source code of The Calculator

{
  "description": "Small spreadsheet to calculate amounts",
  "manifest_version": 2,
  "name": "TheCalculator",
  "version": "1.0",
  "icons": {
    "48": "logo.png"
  },
  "browser_action": {
    "default_icon": "logo.png",
    "default_title": "Thecalculator",
    "default_popup": "thecalculator.html"
  },
  "applications": {
    "gecko": {
      "id": "thecalculator@example.com"
    }
  }
}