Examine source code of Save Page Button

{
  "manifest_version": 2,
  "name": "Save Page Button",
  "version": "1.0",
  "description": "Save your favorite webpages for later reference.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{7038b3b5-5db2-4e58-8e9e-c58679114cba}"
    }
  }
}