tracing: split out ThreadLocalEventBuffer

base/trace_event/thread_local_event_buffer.h

Index: base/trace_event/thread_local_event_buffer.h
diff --git a/base/trace_event/thread_local_event_buffer.h b/base/trace_event/thread_local_event_buffer.h
new file mode 100644
index 0000000000000000000000000000000000000000..274638ed5b1f8f7cc52955dbea64b48a7e3a9978
--- /dev/null
+++ b/base/trace_event/thread_local_event_buffer.h
@@ -0,0 +1,44 @@
+ // Copyright 2016 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 BASE_TRACE_EVENT_THREAD_LOCAL_EVENT_BUFFER_H_
+#define BASE_TRACE_EVENT_THREAD_LOCAL_EVENT_BUFFER_H_
+
+#include <memory>
+
+#include "base/base_export.h"
+#include "base/macros.h"
+#include "base/threading/thread_checker.h"
+
+namespace base {
+namespace trace_event {
+
+class TraceBufferChunk;
+struct TraceEventHandle;
+class TraceEvent;
+
+class BASE_EXPORT ThreadLocalEventBuffer {
+ public:
+  ThreadLocalEventBuffer(int generation);
+  ~ThreadLocalEventBuffer();
+
+  TraceEvent* AddTraceEvent(TraceEventHandle* handle);
+  TraceEvent* GetEventByHandle(TraceEventHandle handle);
+  void Flush();
+  int generation() const { return generation_; }
+  TraceBufferChunk* chunk() const { return chunk_.get(); }
+
+ private:
+  std::unique_ptr<TraceBufferChunk> chunk_;
+  ThreadChecker thread_checker_;
+  size_t chunk_index_;
+  const int generation_;
+
+  DISALLOW_COPY_AND_ASSIGN(ThreadLocalEventBuffer);
+};
+
+}  // namespace trace_event
+}  // namespace base
+
+#endif  // BASE_TRACE_EVENT_THREAD_LOCAL_EVENT_BUFFER_H_