diff -r 000000000000 -r 6474c204b198 security/manager/pki/src/nsNSSDialogHelper.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/security/manager/pki/src/nsNSSDialogHelper.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,55 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsNSSDialogHelper.h"
+#include "nsIWindowWatcher.h"
+#include "nsCOMPtr.h"
+#include "nsIComponentManager.h"
+#include "nsIServiceManager.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "mozilla/dom/ScriptSettings.h"
+
+static const char kOpenDialogParam[] = "centerscreen,chrome,modal,titlebar";
+static const char kOpenWindowParam[] = "centerscreen,chrome,titlebar";
+
+nsresult
+nsNSSDialogHelper::openDialog(
+    nsIDOMWindow *window,
+    const char *url,
+    nsISupports *params,
+    bool modal)
+{
+  nsresult rv;
+  nsCOMPtr<nsIWindowWatcher> windowWatcher = 
+           do_GetService(NS_WINDOWWATCHER_CONTRACTID, &rv);
+  if (NS_FAILED(rv)) return rv;
+
+  nsCOMPtr<nsIDOMWindow> parent = window;
+
+  if (!parent) {
+    windowWatcher->GetActiveWindow(getter_AddRefs(parent));
+  }
+
+  // We're loading XUL into this window, and it's happening on behalf of the
+  // system, not on behalf of content. Make sure the initial about:blank window
+  // gets a system principal, otherwise we'll bork when trying to wrap the
+  // nsIKeyGenThread |arguments| property into the unprivileged scoope.
+  MOZ_ASSERT(!strncmp("chrome://", url, strlen("chrome://")));
+  mozilla::dom::AutoNoJSAPI nojsapi;
+
+  nsCOMPtr<nsIDOMWindow> newWindow;
+  rv = windowWatcher->OpenWindow(parent,
+                                 url,
+                                 "_blank",
+                                 modal
+                                 ? kOpenDialogParam
+                                 : kOpenWindowParam,
+                                 params,
+                                 getter_AddRefs(newWindow));
+  return rv;
+}
+