diff -r 000000000000 -r 6474c204b198 dom/events/BeforeUnloadEvent.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/events/BeforeUnloadEvent.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,48 @@
+/* -*- 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 "mozilla/dom/BeforeUnloadEvent.h"
+
+namespace mozilla {
+namespace dom {
+
+NS_IMPL_ADDREF_INHERITED(BeforeUnloadEvent, Event)
+NS_IMPL_RELEASE_INHERITED(BeforeUnloadEvent, Event)
+
+NS_INTERFACE_MAP_BEGIN(BeforeUnloadEvent)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMBeforeUnloadEvent)
+NS_INTERFACE_MAP_END_INHERITING(Event)
+
+NS_IMETHODIMP
+BeforeUnloadEvent::SetReturnValue(const nsAString& aReturnValue)
+{
+  mText = aReturnValue;
+  return NS_OK;  // Don't throw an exception
+}
+
+NS_IMETHODIMP
+BeforeUnloadEvent::GetReturnValue(nsAString& aReturnValue)
+{
+  aReturnValue = mText;
+  return NS_OK;  // Don't throw an exception
+}
+
+} // namespace dom
+} // namespace mozilla
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+nsresult
+NS_NewDOMBeforeUnloadEvent(nsIDOMEvent** aInstancePtrResult,
+                           EventTarget* aOwner,
+                           nsPresContext* aPresContext,
+                           WidgetEvent* aEvent) 
+{
+  BeforeUnloadEvent* it = new BeforeUnloadEvent(aOwner, aPresContext, aEvent);
+  NS_ADDREF(it);
+  *aInstancePtrResult = static_cast<Event*>(it);
+  return NS_OK;
+}