Create registration context

create-registration-context.js

var createNewRegistrationContext = (function() {
  // This is slow and means using more memory keeping the iframe window alive,
  // but there's no other way to get a fresh registration context. :(
  var iframe = document.createElement("iframe");
  iframe.style.display = "none";
  document.documentElement.appendChild(iframe);
  var lastDocument = iframe.contentDocument;
  return function() {
    // This keeps nesting template documents to create new registration
    // contexts.
    lastDocument = lastDocument.createElement("template").content.
      ownerDocument.implementation.createHTMLDocument(null);
    return lastDocument;
  };
})();