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")
+
+protos = [

[Primiano Tucci (use gerrit), 2016/08/26 14:27:32]

Oh I see what you are doing here, but I'd explicitly list them in the sources.
The thing is for the golden protos we need only event_chunk.proto, while for the
tracing_protos we will need all events and args.

+  "event.proto",
+  "events_chunk.proto",
+]
+
+# Stubs generated using custom plugin.
+proto_library("tracing_protos") {
+  visibility = [ "//components/tracing/*" ]
+
+  proto_in_dir = "."
+  sources = protos
+
+  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++ and Python stubs.
+proto_library("tracing_protos_golden") {
+  visibility = [ "//components/tracing/*" ]
+
+  proto_in_dir = "."
+  sources = protos
+}