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diff --git a/Source/JavaScriptCore/heap/FreeList.h b/Source/JavaScriptCore/heap/FreeList.h
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+++ b/Source/JavaScriptCore/heap/FreeList.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/PrintStream.h>
+
+namespace JSC {
+
+struct FreeCell {
+    FreeCell* next;
+};
+        
+// This representation of a FreeList is convenient for the MarkedAllocator.
+
+struct FreeList {
+    FreeCell* head { nullptr };
+    char* payloadEnd { nullptr };
+    unsigned remaining { 0 };
+    unsigned originalSize { 0 };
+    
+    FreeList()
+    {
+    }
+    
+    static FreeList list(FreeCell* head, unsigned bytes)
+    {
+        FreeList result;
+        result.head = head;
+        result.remaining = 0;
+        result.originalSize = bytes;
+        return result;
+    }
+    
+    static FreeList bump(char* payloadEnd, unsigned remaining)
+    {
+        FreeList result;
+        result.payloadEnd = payloadEnd;
+        result.remaining = remaining;
+        result.originalSize = remaining;
+        return result;
+    }
+    
+    bool operator==(const FreeList& other) const
+    {
+        return head == other.head
+            && payloadEnd == other.payloadEnd
+            && remaining == other.remaining
+            && originalSize == other.originalSize;
+    }
+    
+    bool operator!=(const FreeList& other) const
+    {
+        return !(*this == other);
+    }
+    
+    explicit operator bool() const
+    {
+        return *this != FreeList();
+    }
+    
+    bool allocationWillFail() const { return !head && !remaining; }
+    bool allocationWillSucceed() const { return !allocationWillFail(); }
+    
+    void dump(PrintStream&) const;
+};
+
+} // namespace JSC
+