Examine source code of Full Page1 Capture

{
  "manifest_version": 2,
  "name": "Full Page Capture",
  "version": "1.0",
  "description": "Scroll and stitch the current tab into a single full-page screenshot (PNG).",
  "permissions": [
    "activeTab",
    "tabs",
    "downloads"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "128": "icon128.png"
    }
  },
  "icons": {
    "128": "icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a3240c86-8a9a-4d3b-ba8e-36dd2a0a26c2}"
    }
  }
}