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diff --git a/Source/WTF/wtf/StackStats.h b/Source/WTF/wtf/StackStats.h
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+/*
+ * Copyright (C) 2012 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. 
+ */
+
+#ifndef StackStats_h
+#define StackStats_h
+
+#include "ExportMacros.h"
+#include "ThreadingPrimitives.h"
+
+
+// Define this flag to enable Stack stats collection. This feature is useful
+// for getting a sample of native stack usage sizes.
+//
+// Enabling this will cause stats to be collected and written to a log file at
+// various  instrumented points in the code. It will result in noticeable
+// performance loss. Hence, this should only be enable when you want to do
+// some stats location in your local build. This code is provided here as a
+// convenience for collecting that data. It is not meant to be enabled by
+// default on release or debug builds.
+
+// #define ENABLE_STACK_STATS 1
+
+
+namespace WTF {
+
+#if !ENABLE(STACK_STATS) 
+
+class StackStats {
+public:
+    // The CheckPoint class is for marking check points corresponding
+    // each location in code where a stack recursion check is being done.
+
+    class CheckPoint {
+    public:
+        CheckPoint() { }
+    };
+
+    class PerThreadStats {
+    public:
+        PerThreadStats() { }
+    };
+
+    class LayoutCheckPoint {
+    public:
+        LayoutCheckPoint() { }
+    };
+
+    static void initialize() { }
+    static void probe() { }
+};
+
+#else // ENABLE(STACK_STATS)
+
+class StackStats {
+public:
+    // The CheckPoint class is for marking check points corresponding
+    // each location in code where a stack recursion check is being done.
+
+    class CheckPoint {
+    public:
+        CheckPoint();
+        ~CheckPoint();
+    private:
+        CheckPoint* m_prev;
+    };
+
+    class PerThreadStats {
+    public:
+        PerThreadStats();
+
+    private:
+        int m_reentryDepth;
+        char* m_stackStart;
+        CheckPoint* m_currentCheckPoint;
+
+        friend class CheckPoint;
+        friend class StackStats;
+    };
+
+    class LayoutCheckPoint {
+    public:
+        WTF_EXPORT_PRIVATE LayoutCheckPoint();
+        WTF_EXPORT_PRIVATE ~LayoutCheckPoint();
+
+    private:
+        LayoutCheckPoint* m_prev;
+        int m_depth;
+    };
+
+    // Initializes locks and the log file. Should only be called once.
+    static void initialize();
+
+    // Used for probing the stack at places where we suspect to be high
+    // points of stack usage but are NOT check points where stack recursion
+    // is checked.
+    //
+    // The more places where we add this probe, the more accurate our
+    // stats data will be. However, adding too many probes will also
+    // result in unnecessary performance loss. So, only add these probes
+    // judiciously where appropriate.
+    static void probe();
+
+private:
+    // CheckPoint management:
+    static Mutex* s_sharedLock;
+    static CheckPoint* s_topCheckPoint;
+    static LayoutCheckPoint* s_firstLayoutCheckPoint;
+    static LayoutCheckPoint* s_topLayoutCheckPoint;
+
+    // High watermark stats:
+    static int s_maxCheckPointDiff;
+    static int s_maxStackHeight;
+    static int s_maxReentryDepth;
+
+    static int s_maxLayoutCheckPointDiff;
+    static int s_maxTotalLayoutCheckPointDiff;
+    static int s_maxLayoutReentryDepth;
+
+    friend class CheckPoint;
+    friend class LayoutCheckPoint;
+};
+
+#endif // ENABLE(STACK_STATS) 
+
+} // namespace WTF
+
+using WTF::StackStats;
+
+#endif // StackStats_h