sync: Buffer Protocol Events for about:sync page

sync/internal_api/protocol_event_buffer.h

Index: sync/internal_api/protocol_event_buffer.h
diff --git a/sync/internal_api/protocol_event_buffer.h b/sync/internal_api/protocol_event_buffer.h
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+// 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 SYNC_INTERNAL_API_PROTOCOL_EVENT_BUFFER_H_
+#define SYNC_INTERNAL_API_PROTOCOL_EVENT_BUFFER_H_
+
+#include <deque>
+
+#include "base/memory/scoped_vector.h"
+#include "sync/base/sync_export.h"
+
+namespace syncer {
+
+class ProtocolEvent;
+
+// A container for ProtocolEvents.
+//
+// Stores at most kBufferSize events, then starts dropping the oldest events.
+class SYNC_EXPORT_PRIVATE ProtocolEventBuffer {
+ public:
+  static const size_t kBufferSize;
+
+  ProtocolEventBuffer();
+  ~ProtocolEventBuffer();
+
+  // Records an event.  May cause the oldest event to be dropped.
+  void RecordProtocolEvent(const ProtocolEvent& event);
+
+  // Returns the buffered contents.  Will not clear the buffer.
+  ScopedVector<ProtocolEvent> GetBufferedProtocolEvents() const;
+
+ private:
+  std::deque<ProtocolEvent*> buffer_;
+  STLElementDeleter<std::deque<ProtocolEvent*> > buffer_deleter_;
+
+  DISALLOW_COPY_AND_ASSIGN(ProtocolEventBuffer);
+};
+
+}  // namespace syncer
+
+#endif  // SYNC_INTERNAL_API_PROTOCOL_EVENT_BUFFER_H_