diff -r 000000000000 -r 6474c204b198 embedding/components/windowwatcher/src/nsAutoWindowStateHelper.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/embedding/components/windowwatcher/src/nsAutoWindowStateHelper.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,71 @@
+/* -*- 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 "nsAutoWindowStateHelper.h"
+
+#include "mozilla/dom/Event.h"
+#include "nsIDocument.h"
+#include "nsIDOMEvent.h"
+#include "nsIDOMWindow.h"
+#include "nsPIDOMWindow.h"
+#include "nsString.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+/****************************************************************
+ ****************** nsAutoWindowStateHelper *********************
+ ****************************************************************/
+
+nsAutoWindowStateHelper::nsAutoWindowStateHelper(nsPIDOMWindow *aWindow)
+  : mWindow(aWindow),
+    mDefaultEnabled(DispatchEventToChrome("DOMWillOpenModalDialog"))
+{
+  if (mWindow) {
+    mWindow->EnterModalState();
+  }
+}
+
+nsAutoWindowStateHelper::~nsAutoWindowStateHelper()
+{
+  if (mWindow) {
+    mWindow->LeaveModalState();
+  }
+
+  if (mDefaultEnabled) {
+    DispatchEventToChrome("DOMModalDialogClosed");
+  }
+}
+
+bool
+nsAutoWindowStateHelper::DispatchEventToChrome(const char *aEventName)
+{
+  // XXXbz should we skip dispatching the event if the inner changed?
+  // That is, should we store both the inner and the outer?
+  if (!mWindow) {
+    return true;
+  }
+
+  // The functions of nsContentUtils do not provide the required behavior,
+  // so the following is inlined.
+  nsIDocument* doc = mWindow->GetExtantDoc();
+  if (!doc) {
+    return true;
+  }
+
+  ErrorResult rv;
+  nsRefPtr<Event> event = doc->CreateEvent(NS_LITERAL_STRING("Events"), rv);
+  if (rv.Failed()) {
+    return false;
+  }
+  NS_ENSURE_TRUE(NS_SUCCEEDED(event->InitEvent(NS_ConvertASCIItoUTF16(aEventName), true, true)), false);
+  event->SetTrusted(true);
+  event->GetInternalNSEvent()->mFlags.mOnlyChromeDispatch = true;
+
+  nsCOMPtr<EventTarget> target = do_QueryInterface(mWindow);
+  bool defaultActionEnabled;
+  target->DispatchEvent(event, &defaultActionEnabled);
+  return defaultActionEnabled;
+}