diff -r 000000000000 -r 6474c204b198 widget/xpwidgets/nsClipboardPrivacyHandler.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/widget/xpwidgets/nsClipboardPrivacyHandler.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,124 @@
+/* -*- 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/ArrayUtils.h"
+
+#include "nsClipboardPrivacyHandler.h"
+#include "nsITransferable.h"
+#include "nsISupportsPrimitives.h"
+#include "nsIObserverService.h"
+#include "nsIClipboard.h"
+#include "nsComponentManagerUtils.h"
+#include "nsServiceManagerUtils.h"
+#include "nsLiteralString.h"
+#include "nsNetCID.h"
+#include "nsXPCOM.h"
+#include "mozilla/Services.h"
+
+#if defined(XP_WIN)
+#include <ole2.h>
+#endif
+
+using namespace mozilla;
+
+#define NS_MOZ_DATA_FROM_PRIVATEBROWSING "application/x-moz-private-browsing"
+
+NS_IMPL_ISUPPORTS(nsClipboardPrivacyHandler, nsIObserver, nsISupportsWeakReference)
+
+nsresult
+nsClipboardPrivacyHandler::Init()
+{
+  nsCOMPtr<nsIObserverService> observerService =
+    mozilla::services::GetObserverService();
+  if (!observerService)
+    return NS_ERROR_FAILURE;
+  return observerService->AddObserver(this, "last-pb-context-exited", true);
+}
+
+/**
+  * Prepare the transferable object to be inserted into the clipboard
+  *
+  */
+nsresult
+nsClipboardPrivacyHandler::PrepareDataForClipboard(nsITransferable * aTransferable)
+{
+  NS_ASSERTION(aTransferable, "clipboard given a null transferable");
+
+  bool isPrivateData = false;
+  aTransferable->GetIsPrivateData(&isPrivateData);
+
+  nsresult rv = NS_OK;
+  if (isPrivateData) {
+    nsCOMPtr<nsISupportsPRBool> data = do_CreateInstance(NS_SUPPORTS_PRBOOL_CONTRACTID);
+    if (data) {
+      rv = data->SetData(true);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      // Ignore the error code of AddDataFlavor, since we might have added
+      // this flavor before.  If this call really fails, so will the next
+      // one (SetTransferData).
+      aTransferable->AddDataFlavor(NS_MOZ_DATA_FROM_PRIVATEBROWSING);
+
+      rv = aTransferable->SetTransferData(NS_MOZ_DATA_FROM_PRIVATEBROWSING, data, sizeof(bool));
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsClipboardPrivacyHandler::Observe(nsISupports *aSubject, char const *aTopic, char16_t const *aData)
+{
+  nsresult rv;
+  nsCOMPtr<nsIClipboard> clipboard =
+    do_GetService("@mozilla.org/widget/clipboard;1", &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  const char * flavors[] = { NS_MOZ_DATA_FROM_PRIVATEBROWSING };
+  bool haveFlavors;
+  rv = clipboard->HasDataMatchingFlavors(flavors,
+                                         ArrayLength(flavors),
+                                         nsIClipboard::kGlobalClipboard,
+                                         &haveFlavors);
+  if (NS_SUCCEEDED(rv) && haveFlavors) {
+#if defined(XP_WIN)
+    // Workaround for bug 518412.  On Windows 7 x64, there is a bug
+    // in handling clipboard data without any formats between
+    // 32-bit/64-bit boundaries, which could lead Explorer to crash.
+    // We work around the problem by clearing the clipboard using
+    // the usual Win32 API.
+    NS_ENSURE_TRUE(SUCCEEDED(::OleSetClipboard(nullptr)), NS_ERROR_FAILURE);
+#else
+    // Empty the native clipboard by copying an empty transferable
+    nsCOMPtr<nsITransferable> nullData =
+      do_CreateInstance("@mozilla.org/widget/transferable;1", &rv);
+    NS_ENSURE_SUCCESS(rv, rv);
+    nullData->Init(nullptr);
+    rv = clipboard->SetData(nullData, nullptr,
+                            nsIClipboard::kGlobalClipboard);
+    NS_ENSURE_SUCCESS(rv, rv);
+#endif
+  }
+
+  return NS_OK;
+}
+
+nsresult
+NS_NewClipboardPrivacyHandler(nsClipboardPrivacyHandler ** aHandler)
+{
+  NS_PRECONDITION(aHandler != nullptr, "null ptr");
+  if (!aHandler)
+    return NS_ERROR_NULL_POINTER;
+
+  *aHandler = new nsClipboardPrivacyHandler();
+
+  NS_ADDREF(*aHandler);
+  nsresult rv = (*aHandler)->Init();
+  if (NS_FAILED(rv))
+    NS_RELEASE(*aHandler);
+
+  return rv;
+}