Add tracing service and make the shell+sky_viewer+services talk to it

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/files/file_path.h"
+
+namespace tracing {
+
+class TraceDataSink {
+ public:
+  explicit TraceDataSink(base::FilePath base_name);
+  ~TraceDataSink();
+
+  void AddChunk(const std::string& json);
+  void Flush();
+
+ private:
+  FILE* file_;
+  bool empty_;
+
+  DISALLOW_COPY_AND_ASSIGN(TraceDataSink);
+};
+
+}  // namespace tracing
+
+#endif  // SERVICES_TRACING_TRACE_DATA_SINK_H_