Tracing V2: Trace buffer writer uses proto.

components/tracing/proto/BUILD.gn

+# 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.
+
+import("//third_party/protobuf/proto_library.gni")
+
+# Stubs generated using custom plugin.
+proto_library("protos") {
+  visibility = [ "//components/tracing/*" ]
+
+  proto_in_dir = "."
+  sources = [
+    "event.proto",
+    "events_chunk.proto",
+  ]
+
+  generator_plugin_label =
+      "//components/tracing/tools/proto_zero_plugin:proto_zero_plugin"
+  generator_plugin_suffix = ".pbzero"
+  generator_plugin_options = "wrapper_namespace=pbzero"
+  generate_cc = false
+  generate_python = false
+}
+
+# Official protobuf C++ stubs to test conformance.
+proto_library("golden_protos_for_tests") {
+  visibility = [ "//components/tracing/*" ]
+  testonly = true
+
+  proto_in_dir = "."
+  proto_out_dir = "components/tracing/test/golden_protos"
+  sources = [
+    "events_chunk.proto",
+  ]
+
+  generate_python = false
+}