Generate trace header/footer in tracing consumer instead of service

services/tracing/trace_data_sink.cc

 // 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.
 
 #include "services/tracing/trace_data_sink.h"
 
 #include "base/logging.h"
 #include "mojo/common/data_pipe_utils.h"
 
 using mojo::common::BlockingCopyFromString;
 
 namespace tracing {
-namespace {
-
-const char kStart[] = "{\"traceEvents\":[";
-const char kEnd[] = "]}";
-
-}  // namespace
 
 TraceDataSink::TraceDataSink(mojo::ScopedDataPipeProducerHandle pipe)
     : pipe_(pipe.Pass()), empty_(true) {
-  BlockingCopyFromString(kStart, pipe_);
 }
 
 TraceDataSink::~TraceDataSink() {
   if (pipe_.is_valid())
-    Flush();
+    pipe_.reset();
   DCHECK(!pipe_.is_valid());
 }
 
 void TraceDataSink::AddChunk(const std::string& json) {
   if (!empty_)
     BlockingCopyFromString(",", pipe_);
   empty_ = false;
   BlockingCopyFromString(json, pipe_);
 }
 
-void TraceDataSink::Flush() {
-  BlockingCopyFromString(kEnd, pipe_);
-  pipe_.reset();
-}
-
 }  // namespace tracing