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diff --git a/Source/WTF/wtf/RecursiveLockAdapter.h b/Source/WTF/wtf/RecursiveLockAdapter.h
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+++ b/Source/WTF/wtf/RecursiveLockAdapter.h
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+/*
+ * Copyright (C) 2016 Apple Inc.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
+ */
+
+#pragma once
+
+#include <wtf/Threading.h>
+
+namespace WTF {
+
+template<typename LockType>
+class RecursiveLockAdapter {
+public:
+    RecursiveLockAdapter()
+    {
+    }
+    
+    void lock()
+    {
+        ThreadIdentifier me = currentThread();
+        if (me == m_owner) {
+            m_recursionCount++;
+            return;
+        }
+        
+        m_lock.lock();
+        ASSERT(!m_owner);
+        ASSERT(!m_recursionCount);
+        m_owner = me;
+        m_recursionCount = 1;
+    }
+    
+    void unlock()
+    {
+        if (--m_recursionCount)
+            return;
+        m_owner = 0;
+        m_lock.unlock();
+    }
+    
+    bool tryLock()
+    {
+        ThreadIdentifier me = currentThread();
+        if (me == m_owner) {
+            m_recursionCount++;
+            return true;
+        }
+        
+        if (!m_lock.tryLock())
+            return false;
+        
+        ASSERT(!m_owner);
+        ASSERT(!m_recursionCount);
+        m_owner = me;
+        m_recursionCount = 1;
+        return true;
+    }
+    
+    bool isLocked() const
+    {
+        return m_lock.isLocked();
+    }
+    
+private:
+    ThreadIdentifier m_owner { 0 };
+    unsigned m_recursionCount { 0 };
+    LockType m_lock;
+};
+
+} // namespace WTF
+
+