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diff --git a/Source/WTF/wtf/DeprecatedOptional.h b/Source/WTF/wtf/DeprecatedOptional.h
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+++ b/Source/WTF/wtf/DeprecatedOptional.h
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+/*
+ * Copyright (C) 2014, 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. AND ITS 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 APPLE INC. OR ITS 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.
+ */
+
+// This file contains a deprecated version of WTF::Optional which a released
+// version of Safari uses. Once Safari stops using this, we can remove this.
+// New code should use std::optional.
+
+#pragma once
+
+#include <type_traits>
+
+namespace WTF {
+
+template<typename T>
+class Optional {
+public:
+    explicit operator bool() const { return m_isEngaged; }
+    T& value() { return *asPtr(); }
+
+private:
+    T* asPtr() { return reinterpret_cast<T*>(&m_value); }
+
+    bool m_isEngaged;
+    typename std::aligned_storage<sizeof(T), std::alignment_of<T>::value>::type m_value;
+};
+
+template<typename T> using DeprecatedOptional = WTF::Optional<T>;
+
+} // namespace WTF