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diff --git a/Source/JavaScriptCore/runtime/ClonedArguments.h b/Source/JavaScriptCore/runtime/ClonedArguments.h
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+++ b/Source/JavaScriptCore/runtime/ClonedArguments.h
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+/*
+ * Copyright (C) 2015-2016 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 "ArgumentsMode.h"
+#include "JSObject.h"
+
+namespace JSC {
+
+// This is an Arguments-class object that we create when you do function.arguments, or you say
+// "arguments" inside a function in strict mode. It behaves almpst entirely like an ordinary
+// JavaScript object. All of the arguments values are simply copied from the stack (possibly via
+// some sophisticated ValueRecovery's if an optimizing compiler is in play) and the appropriate
+// properties of the object are populated. The only reason why we need a special class is to make
+// the object claim to be "Arguments" from a toString standpoint, and to avoid materializing the
+// caller/callee/@@iterator properties unless someone asks for them.
+class ClonedArguments : public JSNonFinalObject {
+public:
+    typedef JSNonFinalObject Base;
+    static const unsigned StructureFlags = Base::StructureFlags | OverridesGetOwnPropertySlot | OverridesGetPropertyNames;
+    
+private:
+    ClonedArguments(VM&, Structure*, Butterfly*);
+
+public:
+    static ClonedArguments* createEmpty(VM&, Structure*, JSFunction* callee, unsigned length);
+    static ClonedArguments* createEmpty(ExecState*, JSFunction* callee, unsigned length);
+    static ClonedArguments* createWithInlineFrame(ExecState* myFrame, ExecState* targetFrame, InlineCallFrame*, ArgumentsMode);
+    static ClonedArguments* createWithMachineFrame(ExecState* myFrame, ExecState* targetFrame, ArgumentsMode);
+    static ClonedArguments* createByCopyingFrom(ExecState*, Structure*, Register* argumentsStart, unsigned length, JSFunction* callee);
+    
+    static Structure* createStructure(VM&, JSGlobalObject*, JSValue prototype);
+    static Structure* createSlowPutStructure(VM&, JSGlobalObject*, JSValue prototype);
+
+    static void visitChildren(JSCell*, SlotVisitor&);
+
+    DECLARE_INFO;
+
+private:
+    static Structure* createStructure(VM&, JSGlobalObject*, JSValue prototype, IndexingType);
+
+    static bool getOwnPropertySlot(JSObject*, ExecState*, PropertyName, PropertySlot&);
+    static void getOwnPropertyNames(JSObject*, ExecState*, PropertyNameArray&, EnumerationMode);
+    static bool put(JSCell*, ExecState*, PropertyName, JSValue, PutPropertySlot&);
+    static bool deleteProperty(JSCell*, ExecState*, PropertyName);
+    static bool defineOwnProperty(JSObject*, ExecState*, PropertyName, const PropertyDescriptor&, bool shouldThrow);
+    
+    bool specialsMaterialized() const { return !m_callee; }
+    void materializeSpecials(ExecState*);
+    void materializeSpecialsIfNecessary(ExecState*);
+    
+    WriteBarrier<JSFunction> m_callee; // Set to nullptr when we materialize all of our special properties.
+};
+
+static const PropertyOffset clonedArgumentsLengthPropertyOffset = 100;
+
+} // namespace JSC