Imported WebKit commit 2ea9d364d0f6efa8fa64acf19f451504c59be0e4 (http://svn.webkit.org/repository/webkit/trunk@104285)

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diff --git a/Source/JavaScriptCore/wtf/MessageQueue.h b/Source/JavaScriptCore/wtf/MessageQueue.h
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+/*
+ * Copyright (C) 2008 Apple Inc. All rights reserved.
+ * Copyright (C) 2009 Google 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.
+ * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
+ *     its contributors may be used to endorse or promote products derived
+ *     from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE 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 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 MessageQueue_h
+#define MessageQueue_h
+
+#include <limits>
+#include <wtf/Assertions.h>
+#include <wtf/Deque.h>
+#include <wtf/Noncopyable.h>
+#include <wtf/Threading.h>
+
+namespace WTF {
+
+    enum MessageQueueWaitResult {
+        MessageQueueTerminated,       // Queue was destroyed while waiting for message.
+        MessageQueueTimeout,          // Timeout was specified and it expired.
+        MessageQueueMessageReceived   // A message was successfully received and returned.
+    };
+
+    // The queue takes ownership of messages and transfer it to the new owner
+    // when messages are fetched from the queue.
+    // Essentially, MessageQueue acts as a queue of OwnPtr<DataType>.
+    template<typename DataType>
+    class MessageQueue {
+        WTF_MAKE_NONCOPYABLE(MessageQueue);
+    public:
+        MessageQueue() : m_killed(false) { }
+        ~MessageQueue();
+
+        void append(PassOwnPtr<DataType>);
+        bool appendAndCheckEmpty(PassOwnPtr<DataType>);
+        void prepend(PassOwnPtr<DataType>);
+
+        PassOwnPtr<DataType> waitForMessage();
+        PassOwnPtr<DataType> tryGetMessage();
+        PassOwnPtr<DataType> tryGetMessageIgnoringKilled();
+        template<typename Predicate>
+        PassOwnPtr<DataType> waitForMessageFilteredWithTimeout(MessageQueueWaitResult&, Predicate&, double absoluteTime);
+
+        template<typename Predicate>
+        void removeIf(Predicate&);
+
+        void kill();
+        bool killed() const;
+
+        // The result of isEmpty() is only valid if no other thread is manipulating the queue at the same time.
+        bool isEmpty();
+
+        static double infiniteTime() { return std::numeric_limits<double>::max(); }
+
+    private:
+        static bool alwaysTruePredicate(DataType*) { return true; }
+
+        mutable Mutex m_mutex;
+        ThreadCondition m_condition;
+        Deque<DataType*> m_queue;
+        bool m_killed;
+    };
+
+    template<typename DataType>
+    MessageQueue<DataType>::~MessageQueue()
+    {
+        deleteAllValues(m_queue);
+    }
+
+    template<typename DataType>
+    inline void MessageQueue<DataType>::append(PassOwnPtr<DataType> message)
+    {
+        MutexLocker lock(m_mutex);
+        m_queue.append(message.leakPtr());
+        m_condition.signal();
+    }
+
+    // Returns true if the queue was empty before the item was added.
+    template<typename DataType>
+    inline bool MessageQueue<DataType>::appendAndCheckEmpty(PassOwnPtr<DataType> message)
+    {
+        MutexLocker lock(m_mutex);
+        bool wasEmpty = m_queue.isEmpty();
+        m_queue.append(message.leakPtr());
+        m_condition.signal();
+        return wasEmpty;
+    }
+
+    template<typename DataType>
+    inline void MessageQueue<DataType>::prepend(PassOwnPtr<DataType> message)
+    {
+        MutexLocker lock(m_mutex);
+        m_queue.prepend(message.leakPtr());
+        m_condition.signal();
+    }
+
+    template<typename DataType>
+    inline PassOwnPtr<DataType> MessageQueue<DataType>::waitForMessage()
+    {
+        MessageQueueWaitResult exitReason; 
+        OwnPtr<DataType> result = waitForMessageFilteredWithTimeout(exitReason, MessageQueue<DataType>::alwaysTruePredicate, infiniteTime());
+        ASSERT(exitReason == MessageQueueTerminated || exitReason == MessageQueueMessageReceived);
+        return result.release();
+    }
+
+    template<typename DataType>
+    template<typename Predicate>
+    inline PassOwnPtr<DataType> MessageQueue<DataType>::waitForMessageFilteredWithTimeout(MessageQueueWaitResult& result, Predicate& predicate, double absoluteTime)
+    {
+        MutexLocker lock(m_mutex);
+        bool timedOut = false;
+
+        DequeConstIterator<DataType*> found = m_queue.end();
+        while (!m_killed && !timedOut && (found = m_queue.findIf(predicate)) == m_queue.end())
+            timedOut = !m_condition.timedWait(m_mutex, absoluteTime);
+
+        ASSERT(!timedOut || absoluteTime != infiniteTime());
+
+        if (m_killed) {
+            result = MessageQueueTerminated;
+            return nullptr;
+        }
+
+        if (timedOut) {
+            result = MessageQueueTimeout;
+            return nullptr;
+        }
+
+        ASSERT(found != m_queue.end());
+        OwnPtr<DataType> message = adoptPtr(*found);
+        m_queue.remove(found);
+        result = MessageQueueMessageReceived;
+        return message.release();
+    }
+
+    template<typename DataType>
+    inline PassOwnPtr<DataType> MessageQueue<DataType>::tryGetMessage()
+    {
+        MutexLocker lock(m_mutex);
+        if (m_killed)
+            return nullptr;
+        if (m_queue.isEmpty())
+            return nullptr;
+
+        return adoptPtr(m_queue.takeFirst());
+    }
+
+    template<typename DataType>
+    inline PassOwnPtr<DataType> MessageQueue<DataType>::tryGetMessageIgnoringKilled()
+    {
+        MutexLocker lock(m_mutex);
+        if (m_queue.isEmpty())
+            return nullptr;
+
+        return adoptPtr(m_queue.takeFirst());
+    }
+
+    template<typename DataType>
+    template<typename Predicate>
+    inline void MessageQueue<DataType>::removeIf(Predicate& predicate)
+    {
+        MutexLocker lock(m_mutex);
+        DequeConstIterator<DataType*> found = m_queue.end();
+        while ((found = m_queue.findIf(predicate)) != m_queue.end()) {
+            DataType* message = *found;
+            m_queue.remove(found);
+            delete message;
+        }
+    }
+
+    template<typename DataType>
+    inline bool MessageQueue<DataType>::isEmpty()
+    {
+        MutexLocker lock(m_mutex);
+        if (m_killed)
+            return true;
+        return m_queue.isEmpty();
+    }
+
+    template<typename DataType>
+    inline void MessageQueue<DataType>::kill()
+    {
+        MutexLocker lock(m_mutex);
+        m_killed = true;
+        m_condition.broadcast();
+    }
+
+    template<typename DataType>
+    inline bool MessageQueue<DataType>::killed() const
+    {
+        MutexLocker lock(m_mutex);
+        return m_killed;
+    }
+} // namespace WTF
+
+using WTF::MessageQueue;
+// MessageQueueWaitResult enum and all its values.
+using WTF::MessageQueueWaitResult;
+using WTF::MessageQueueTerminated;
+using WTF::MessageQueueTimeout;
+using WTF::MessageQueueMessageReceived;
+
+#endif // MessageQueue_h