[OBSOLETE] tracing v2: introduce TraceBufferWriter

components/tracing/proto/event_args_for_testing.proto

+// 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.
+
+syntax = "proto2";
+option optimize_for = LITE_RUNTIME;
+
+package tracing.proto;
+
+message EventArgsForTesting {
+  message NestedMessage {
+    optional uint64 uint64_field = 1;
+    optional bytes bytes_field = 100;
+  }
+
+  optional uint32 uint32_field = 1;
+  optional string string_field = 2;
+  repeated NestedMessage nested_fields = 3;
+}