diff -r 000000000000 -r 6474c204b198 security/sandbox/chromium/base/synchronization/lock.cc
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/security/sandbox/chromium/base/synchronization/lock.cc	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,48 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This file is used for debugging assertion support.  The Lock class
+// is functionally a wrapper around the LockImpl class, so the only
+// real intelligence in the class is in the debugging logic.
+
+#if !defined(NDEBUG)
+
+#include "base/synchronization/lock.h"
+#include "base/logging.h"
+
+namespace base {
+
+const PlatformThreadId kNoThreadId = static_cast<PlatformThreadId>(0);
+
+Lock::Lock() : lock_() {
+  owned_by_thread_ = false;
+  owning_thread_id_ = kNoThreadId;
+}
+
+Lock::~Lock() {
+  DCHECK(!owned_by_thread_);
+  DCHECK_EQ(kNoThreadId, owning_thread_id_);
+}
+
+void Lock::AssertAcquired() const {
+  DCHECK(owned_by_thread_);
+  DCHECK_EQ(owning_thread_id_, PlatformThread::CurrentId());
+}
+
+void Lock::CheckHeldAndUnmark() {
+  DCHECK(owned_by_thread_);
+  DCHECK_EQ(owning_thread_id_, PlatformThread::CurrentId());
+  owned_by_thread_ = false;
+  owning_thread_id_ = kNoThreadId;
+}
+
+void Lock::CheckUnheldAndMark() {
+  DCHECK(!owned_by_thread_);
+  owned_by_thread_ = true;
+  owning_thread_id_ = PlatformThread::CurrentId();
+}
+
+}  // namespace base
+
+#endif  // NDEBUG