diff -r 000000000000 -r 6474c204b198 accessible/src/windows/msaa/RootAccessibleWrap.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/accessible/src/windows/msaa/RootAccessibleWrap.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,46 @@
+/* -*- 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 "RootAccessibleWrap.h"
+
+#include "Compatibility.h"
+#include "nsCoreUtils.h"
+#include "nsWinUtils.h"
+
+using namespace mozilla::a11y;
+
+////////////////////////////////////////////////////////////////////////////////
+// Constructor/desctructor
+
+RootAccessibleWrap::
+  RootAccessibleWrap(nsIDocument* aDocument, nsIContent* aRootContent,
+                     nsIPresShell* aPresShell) :
+  RootAccessible(aDocument, aRootContent, aPresShell)
+{
+}
+
+RootAccessibleWrap::~RootAccessibleWrap()
+{
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// RootAccessible
+
+void
+RootAccessibleWrap::DocumentActivated(DocAccessible* aDocument)
+{
+  if (Compatibility::IsDolphin() &&
+      nsCoreUtils::IsTabDocument(aDocument->DocumentNode())) {
+    uint32_t count = mChildDocuments.Length();
+    for (uint32_t idx = 0; idx < count; idx++) {
+      DocAccessible* childDoc = mChildDocuments[idx];
+      HWND childDocHWND = static_cast<HWND>(childDoc->GetNativeWindow());
+      if (childDoc != aDocument)
+        nsWinUtils::HideNativeWindow(childDocHWND);
+      else
+        nsWinUtils::ShowNativeWindow(childDocHWND);
+    }
+  }
+}