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diff --git a/Source/WTF/wtf/OptionSet.h b/Source/WTF/wtf/OptionSet.h
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+++ b/Source/WTF/wtf/OptionSet.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. 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.
+ */
+
+#pragma once
+
+#include <initializer_list>
+#include <iterator>
+#include <type_traits>
+#include <wtf/Assertions.h>
+#include <wtf/MathExtras.h>
+
+namespace WTF {
+
+// OptionSet is a class that represents a set of enumerators in a space-efficient manner. The enumerators
+// must be powers of two greater than 0. This class is useful as a replacement for passing a bitmask of
+// enumerators around.
+template<typename T> class OptionSet {
+    static_assert(std::is_enum<T>::value, "T is not an enum type");
+    typedef typename std::make_unsigned<typename std::underlying_type<T>::type>::type StorageType;
+
+public:
+    template<typename StorageType> class Iterator {
+    public:
+        // Isolate the rightmost set bit.
+        T operator*() const { return static_cast<T>(m_value & -m_value); }
+
+        // Iterates from smallest to largest enum value by turning off the rightmost set bit.
+        Iterator& operator++()
+        {
+            m_value &= m_value - 1;
+            return *this;
+        }
+
+        Iterator& operator++(int) = delete;
+
+        bool operator==(const Iterator& other) const { return m_value == other.m_value; }
+        bool operator!=(const Iterator& other) const { return m_value != other.m_value; }
+
+    private:
+        Iterator(StorageType value) : m_value(value) { }
+        friend OptionSet;
+
+        StorageType m_value;
+    };
+    using iterator = Iterator<StorageType>;
+
+    static constexpr OptionSet fromRaw(StorageType storageType)
+    {
+        return OptionSet(static_cast<T>(storageType), FromRawValue);
+    }
+
+    constexpr OptionSet() = default;
+
+#if ASSERT_DISABLED
+    constexpr OptionSet(T t)
+        : m_storage(static_cast<StorageType>(t))
+    {
+    }
+#else
+    OptionSet(T t)
+        : m_storage(static_cast<StorageType>(t))
+    {
+        ASSERT_WITH_MESSAGE(hasOneBitSet(static_cast<StorageType>(t)), "Enumerator is not a positive power of two.");
+    }
+#endif
+
+    // FIXME: Make this constexpr once we adopt C++14 as C++11 does not support for-loops
+    // in a constexpr function.
+    OptionSet(std::initializer_list<T> initializerList)
+    {
+        for (auto& option : initializerList) {
+            ASSERT_WITH_MESSAGE(hasOneBitSet(static_cast<StorageType>(option)), "Enumerator is not a positive power of two.");
+            m_storage |= static_cast<StorageType>(option);
+        }
+    }
+
+    constexpr StorageType toRaw() const { return m_storage; }
+
+    constexpr bool isEmpty() const { return !m_storage; }
+
+    constexpr iterator begin() const { return m_storage; }
+    constexpr iterator end() const { return 0; }
+
+    constexpr bool contains(OptionSet optionSet) const
+    {
+        return m_storage & optionSet.m_storage;
+    }
+
+    constexpr friend bool operator==(OptionSet lhs, OptionSet rhs)
+    {
+        return lhs.m_storage == rhs.m_storage;
+    }
+
+    constexpr friend bool operator!=(OptionSet lhs, OptionSet rhs)
+    {
+        return lhs.m_storage != rhs.m_storage;
+    }
+
+    friend OptionSet& operator|=(OptionSet& lhs, OptionSet rhs)
+    {
+        lhs.m_storage |= rhs.m_storage;
+
+        return lhs;
+    }
+
+    constexpr friend OptionSet operator-(OptionSet lhs, OptionSet rhs)
+    {
+        return OptionSet::fromRaw(lhs.m_storage & ~rhs.m_storage);
+    }
+
+private:
+    enum InitializationTag { FromRawValue };
+    constexpr OptionSet(T t, InitializationTag)
+        : m_storage(static_cast<StorageType>(t))
+    {
+    }
+    StorageType m_storage { 0 };
+};
+
+}
+
+using WTF::OptionSet;