Examine source code of QRCodeHost

{
  "manifest_version": 2,
  "name": "QR Code - Free Fast Small Simple Secure",
  "short_name": "qrhost",
  "description": "Free, Fast, Small, Simple, Secure. Generates QR code of current page with click or Ctrl+Shift+1",
  "version": "2.1",
  "browser_action": {
    "default_icon": "img/icon128.png",
    "default_title": "Press the button to display QR Code of current tab or Ctrl+Shift+1",
    "default_popup": "popup.html"
  },
  "icons": {
    "16": "img/icon16.png",
    "48": "img/icon48.png",
    "128": "img/icon128.png"
  },
  "permissions": [
    "activeTab"
  ],
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "default": "Ctrl+Shift+1"
      }
    }
  }
}