Prioritizing input and compositor tasks in the blink scheduler.

Source/platform/scheduler/DoubleBufferedDeque.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef DoubleBufferedDeque_h
+#define DoubleBufferedDeque_h
+
+#include "wtf/Deque.h"
+#include "wtf/Noncopyable.h"
+#include "wtf/ThreadingPrimitives.h"
+
+namespace blink {
+
+template <typename T> class DoubleBufferedDeque {
+    WTF_MAKE_NONCOPYABLE(DoubleBufferedDeque);
+public:
+    DoubleBufferedDeque()
+        : m_activeIndex(0) { }
+
+    void append(const T& value)
+    {
+        Locker<Mutex> lock(m_mutex);
+        m_queue[m_activeIndex].append(value);
+    }
+
+    bool isEmpty()
+    {
+        Locker<Mutex> lock(m_mutex);
+        return m_queue[m_activeIndex].isEmpty();
+    }
+
+    WTF::Deque<T>& swapBuffers()
+    {
+        Locker<Mutex> lock(m_mutex);
+        int oldIndex = m_activeIndex;
+        m_activeIndex ^= 1;
+        ASSERT(m_queue[m_activeIndex].isEmpty());
+        return m_queue[oldIndex];
+    }
+
+private:
+    WTF::Deque<T> m_queue[2];
+    int m_activeIndex;
+    Mutex m_mutex;
+};
+
+} // namespace blink
+
+#endif // DoubleBufferedDeque_h