Generate trace header/footer in tracing consumer instead of service

services/tracing/trace_data_sink.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 SERVICES_TRACING_TRACE_DATA_SINK_H_
 #define SERVICES_TRACING_TRACE_DATA_SINK_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "mojo/public/cpp/system/data_pipe.h"
 
 namespace tracing {
 
 class TraceDataSink {
  public:
   explicit TraceDataSink(mojo::ScopedDataPipeProducerHandle pipe);
   ~TraceDataSink();
 
   void AddChunk(const std::string& json);
-  void Flush();
 
  private:
   mojo::ScopedDataPipeProducerHandle pipe_;
   bool empty_;
 
   DISALLOW_COPY_AND_ASSIGN(TraceDataSink);
 };
 
 }  // namespace tracing
 
 #endif  // SERVICES_TRACING_TRACE_DATA_SINK_H_