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diff --git a/Source/JavaScriptCore/wtf/BloomFilter.h b/Source/JavaScriptCore/wtf/BloomFilter.h
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+++ b/Source/JavaScriptCore/wtf/BloomFilter.h
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+/*
+ * Copyright (C) 2011 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.
+ */
+
+#ifndef BloomFilter_h
+#define BloomFilter_h
+
+#include <wtf/AlwaysInline.h>
+#include <wtf/text/AtomicString.h>
+
+namespace WTF {
+
+// Counting bloom filter with k=2 and 8 bit counters. Uses 2^keyBits bytes of memory.
+// False positive rate is approximately (1-e^(-2n/m))^2, where n is the number of unique 
+// keys and m is the table size (==2^keyBits).
+template <unsigned keyBits>
+class BloomFilter {
+public:
+    COMPILE_ASSERT(keyBits <= 16, bloom_filter_key_size);
+
+    static const size_t tableSize = 1 << keyBits;
+    static const unsigned keyMask = (1 << keyBits) - 1;
+    static uint8_t maximumCount() { return std::numeric_limits<uint8_t>::max(); }
+    
+    BloomFilter() { clear(); }
+
+    void add(unsigned hash);
+    void remove(unsigned hash);
+
+    // The filter may give false positives (claim it may contain a key it doesn't)
+    // but never false negatives (claim it doesn't contain a key it does).
+    bool mayContain(unsigned hash) const { return firstSlot(hash) && secondSlot(hash); }
+    
+    // The filter must be cleared before reuse even if all keys are removed.
+    // Otherwise overflowed keys will stick around.
+    void clear();
+
+    void add(const AtomicString& string) { add(string.impl()->existingHash()); }
+    void add(const String& string) { add(string.impl()->hash()); }
+    void remove(const AtomicString& string) { remove(string.impl()->existingHash()); }
+    void remove(const String& string) { remove(string.impl()->hash()); }
+
+    bool mayContain(const AtomicString& string) const { return mayContain(string.impl()->existingHash()); }
+    bool mayContain(const String& string) const { return mayContain(string.impl()->hash()); }
+
+#if !ASSERT_DISABLED
+    // Slow.
+    bool likelyEmpty() const;
+    bool isClear() const;
+#endif
+
+private:
+    uint8_t& firstSlot(unsigned hash) { return m_table[hash & keyMask]; }
+    uint8_t& secondSlot(unsigned hash) { return m_table[(hash >> 16) & keyMask]; }
+    const uint8_t& firstSlot(unsigned hash) const { return m_table[hash & keyMask]; }
+    const uint8_t& secondSlot(unsigned hash) const { return m_table[(hash >> 16) & keyMask]; }
+
+    uint8_t m_table[tableSize];
+};
+    
+template <unsigned keyBits>
+inline void BloomFilter<keyBits>::add(unsigned hash)
+{
+    uint8_t& first = firstSlot(hash);
+    uint8_t& second = secondSlot(hash);
+    if (LIKELY(first < maximumCount()))
+        ++first;
+    if (LIKELY(second < maximumCount()))
+        ++second;
+}
+
+template <unsigned keyBits>
+inline void BloomFilter<keyBits>::remove(unsigned hash)
+{
+    uint8_t& first = firstSlot(hash);
+    uint8_t& second = secondSlot(hash);
+    ASSERT(first);
+    ASSERT(second);
+    // In case of an overflow, the slot sticks in the table until clear().
+    if (LIKELY(first < maximumCount()))
+        --first;
+    if (LIKELY(second < maximumCount()))
+        --second;
+}
+    
+template <unsigned keyBits>
+inline void BloomFilter<keyBits>::clear()
+{
+    memset(m_table, 0, tableSize);
+}
+
+#if !ASSERT_DISABLED
+template <unsigned keyBits>
+bool BloomFilter<keyBits>::likelyEmpty() const
+{
+    for (size_t n = 0; n < tableSize; ++n) {
+        if (m_table[n] && m_table[n] != maximumCount())
+            return false;
+    }
+    return true;
+}
+
+template <unsigned keyBits>
+bool BloomFilter<keyBits>::isClear() const
+{
+    for (size_t n = 0; n < tableSize; ++n) {
+        if (m_table[n])
+            return false;
+    }
+    return true;
+}
+#endif
+
+}
+
+using WTF::BloomFilter;
+
+#endif