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diff --git a/Source/JavaScriptCore/wtf/ThreadRestrictionVerifier.h b/Source/JavaScriptCore/wtf/ThreadRestrictionVerifier.h
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+++ b/Source/JavaScriptCore/wtf/ThreadRestrictionVerifier.h
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+/*
+ * Copyright (C) 2011 Google 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:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * 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.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "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 THE COPYRIGHT
+ * OWNER 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.
+ */
+
+#ifndef ThreadRestrictionVerifier_h
+#define ThreadRestrictionVerifier_h
+
+#include <wtf/Assertions.h>
+#include <wtf/Threading.h>
+#include <wtf/ThreadingPrimitives.h>
+
+#if HAVE(DISPATCH_H)
+#include <dispatch/dispatch.h>
+#endif
+
+#ifndef NDEBUG
+
+namespace WTF {
+
+// Verifies that a class is used in a way that respects its lack of thread-safety.
+// The default mode is to verify that the object will only be used on a single thread. The
+// thread gets captured when setShared(true) is called.
+// The mode may be changed by calling useMutexMode (or turnOffVerification).
+class ThreadRestrictionVerifier {
+public:
+    ThreadRestrictionVerifier()
+        : m_mode(SingleThreadVerificationMode)
+        , m_shared(false)
+        , m_owningThread(0)
+        , m_mutex(0)
+#if HAVE(DISPATCH_H)
+        , m_owningQueue(0)
+#endif
+    {
+    }
+
+#if HAVE(DISPATCH_H)
+    ~ThreadRestrictionVerifier()
+    {
+        if (m_owningQueue)
+            dispatch_release(m_owningQueue);
+    }
+#endif
+
+    void setMutexMode(Mutex& mutex)
+    {
+        ASSERT(m_mode == SingleThreadVerificationMode || (m_mode == MutexVerificationMode && &mutex == m_mutex));
+        m_mode = MutexVerificationMode;
+        m_mutex = &mutex;
+    }
+
+#if HAVE(DISPATCH_H)
+    void setDispatchQueueMode(dispatch_queue_t queue)
+    {
+        ASSERT(m_mode == SingleThreadVerificationMode);
+        m_mode = SingleDispatchQueueVerificationMode;
+        m_owningQueue = queue;
+        dispatch_retain(m_owningQueue);
+    }
+#endif
+
+    void turnOffVerification()
+    {
+        ASSERT(m_mode == SingleThreadVerificationMode);
+        m_mode = NoVerificationMode;
+    }
+
+    // Indicates that the object may (or may not) be owned by more than one place.
+    void setShared(bool shared)
+    {
+#if !ASSERT_DISABLED
+        bool previouslyShared = m_shared;
+#endif
+        m_shared = shared;
+
+        if (!m_shared)
+            return;
+
+        switch (m_mode) {
+        case SingleThreadVerificationMode:
+            ASSERT(shared != previouslyShared);
+            // Capture the current thread to verify that subsequent ref/deref happen on this thread.
+            m_owningThread = currentThread();
+            return;
+
+#if HAVE(DISPATCH_H)
+        case SingleDispatchQueueVerificationMode:
+#endif
+        case MutexVerificationMode:
+        case NoVerificationMode:
+            return;
+        }
+        ASSERT_NOT_REACHED();
+    }
+
+    // Is it OK to use the object at this moment on the current thread?
+    bool isSafeToUse() const
+    {
+        if (!m_shared)
+            return true;
+
+        switch (m_mode) {
+        case SingleThreadVerificationMode:
+            return m_owningThread == currentThread();
+
+        case MutexVerificationMode:
+            if (!m_mutex->tryLock())
+                return true;
+            m_mutex->unlock();
+            return false;
+
+#if HAVE(DISPATCH_H)
+        case SingleDispatchQueueVerificationMode:
+            return m_owningQueue == dispatch_get_current_queue();
+#endif
+
+        case NoVerificationMode:
+            return true;
+        }
+        ASSERT_NOT_REACHED();
+        return true;
+    }
+
+private:
+    enum VerificationMode {
+        SingleThreadVerificationMode,
+        MutexVerificationMode,
+        NoVerificationMode,
+#if HAVE(DISPATCH_H)
+        SingleDispatchQueueVerificationMode,
+#endif
+    };
+
+    VerificationMode m_mode;
+    bool m_shared;
+
+    // Used by SingleThreadVerificationMode
+    ThreadIdentifier m_owningThread;
+
+    // Used by MutexVerificationMode.
+    Mutex* m_mutex;
+
+#if HAVE(DISPATCH_H)
+    // Used by SingleDispatchQueueVerificationMode.
+    dispatch_queue_t m_owningQueue;
+#endif
+};
+
+}
+
+#endif
+#endif