Examine source code of Gmail Notifier Plus

{
  "manifest_version": 2,
  "name": "Gmail Notifier Plus",
  "version": "1.3",
  "description": "Check unread Gmail messages with badge and notifications.",
  "permissions": [
    "https://mail.google.com/*",
    "notifications"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "default_icon": "icons/logo_64.png",
    "default_popup": "popup.html"
  },
  "icons": {
    "32": "icons/logo_32.png",
    "64": "icons/logo_64.png",
    "128": "icons/logo_128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{05fd6045-dfeb-4133-b892-6c1f99f7198e}"
    }
  }
}