WIP - not ready for review

Source/platform/TimerHeapEntry.h

+// Copyright 2015 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 TimerHeapEntry_h
+#define TimerHeapEntry_h
+
+#include "wtf/Noncopyable.h"
+#include <stddef.h>
+
+namespace blink {
+
+class TimerBase;
+class TimerHeap;
+
+// TimerHeapEntry is all of the state TimerHeap maintains about a
+// timer. Because even repeating timers are only scheduled once (for
+// the next time they're fired) as a result there's only one entry for
+// a timer. For this reason TimerHeapEntry is stored inline as part of
+// the TimerBase.
+class TimerHeapEntry {
+    WTF_MAKE_NONCOPYABLE(TimerHeapEntry);
+public:
+    explicit TimerHeapEntry(TimerHeap*);
+    virtual ~TimerHeapEntry();
+
+    // FIXME: TimerBase uses setValue(0) to mean "not scheduled" but
+    // it may be simpler to make this explicit.
+    double value() const { return m_value; }
+    void setValue(TimerBase&, double newValue);
+
+    bool inHeap() const { return m_state & TimerHeapEntryInHeap; }
+
+private:
+    friend class TimerHeap;
+    friend class TimerHeapLessThanFunction;
+    friend class TimerHeapReference;
+
+    // The heap this entry is in when the timer is scheduled. There's
+    // one timer heap per thread, and timers don't jump threads, so
+    // this is fixed for the life of the timer.
+    TimerHeap* m_owner;
+
+    enum State {
+        TimerHeapEntryNotInHeap,
+        TimerHeapEntryInHeap,
+        TimerHeapEntryInHeap_ForcedMinimumForPopping = 3
+    };
+    State m_state;
+
+    // The next fire time. The timer heap doesn't particularly care
+    // that this is a time; it's just part of the (m_value,
+    // m_heapInsertionOrder) key in the min-heap.
+    double m_value;
+
+    // This is assigned from an incrementing counter. When comparing
+    // entries which have the same m_value, the comparison falls back
+    // to m_heapInsertionOrder which means timers scheduled for the
+    // same time will always fire in the order that they were
+    // scheduled in.
+    size_t m_heapInsertionOrder;
+
+    // If the timer is in the heap, the position of the timer in the
+    // heap.
+    size_t m_heapIndex;
+};
+
+} // namespace blink
+
+#endif // TimerHeapEntry_h