[cros] Add RecursiveLock for CrOS implementation.

rlz/lib/recursive_lock.h

Index: rlz/lib/recursive_lock.h
diff --git a/rlz/lib/recursive_lock.h b/rlz/lib/recursive_lock.h
new file mode 100644
index 0000000000000000000000000000000000000000..43c957472d5c3d05b7826bb95ba40d1c5b980864
--- /dev/null
+++ b/rlz/lib/recursive_lock.h
@@ -0,0 +1,34 @@
+// Copyright (c) 2012 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.
+
+#ifndef RLZ_CHROMEOS_LIB_RECURSIVE_LOCK_H_
+#define RLZ_CHROMEOS_LIB_RECURSIVE_LOCK_H_
+
+#include "base/atomicops.h"
+#include "base/basictypes.h"
+#include "base/synchronization/lock.h"
+
+namespace rlz_lib {
+
+
+class RecursiveLock {
+ public:
+  RecursiveLock();
+  ~RecursiveLock();
+
+  void Acquire();
+  void Release();
+
+ private:
+  // Underlying non-recursive lock.
+  base::Lock lock_;
+  // Owner thread ID.
+  base::subtle::Atomic32 owner_;
+  // Recursion lock depth.
+  int recursion_;
+};
+
+}  // namespace rlz_lib
+
+#endif  // RLZ_CHROMEOS_LIB_RECURSIVE_LOCK_H_