Tracing V2: Proto fields reflection.

components/tracing/BUILD.gn

 # 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.
 
 import("//third_party/protobuf/proto_library.gni")
 
 component("tracing") {
   sources = [
     "child/child_memory_dump_manager_delegate_impl.cc",
     "child/child_memory_dump_manager_delegate_impl.h",
@@ skipping 58 matching lines @@
     "test/example_proto/library.proto",
     "test/example_proto/library_internals/galaxies.proto",
     "test/example_proto/test_messages.proto",
     "test/example_proto/upper_import.proto",
   ]
 
   proto_in_dir = "test/example_proto"
 
   generator_plugin_label = "tools/proto_zero_plugin:proto_zero_plugin"
   generator_plugin_suffix = ".pbzero"
-  generator_plugin_options = "wrapper_namespace=pbzero"
+  generator_plugin_options = "wrapper_namespace=pbzero,reflection=true"

[Primiano Tucci (use gerrit), 2016/09/01 16:18:06]

i'd avoid unnecessary switches. we just need this.
We can add a switch if we end up not needing it.
In general Chrome philosophy is to never overdesign: more codepaths == less
readable code == harder maintenance 

   generate_cc = true
   generate_python = false
 }
 
 source_set("unit_tests") {
   testonly = true
 
   sources = [
     "child/child_trace_message_filter_unittest.cc",
     "common/graphics_memory_dump_provider_android_unittest.cc",
     "common/process_metrics_memory_dump_provider_unittest.cc",
     "core/proto_utils_unittest.cc",
     "core/proto_zero_message_unittest.cc",
     "core/scattered_stream_writer_unittest.cc",
     "core/trace_buffer_writer_unittest.cc",
     "core/trace_ring_buffer_unittest.cc",
     "test/fake_scattered_buffer.cc",
     "test/proto_zero_generation_unittest.cc",
   ]
 
   deps = [
     ":proto_zero_testing_messages",
     ":tracing",
     "//base/test:test_support",
     "//components/tracing/proto:golden_protos_for_tests",
     "//ipc",
     "//testing/gmock:gmock",
     "//testing/gtest",
+    "//third_party/protobuf:protoc_lib",
   ]
 
   if (!is_android) {
     sources += [ "browser/trace_config_file_unittest.cc" ]
     deps += [ ":startup_tracing" ]
   }
 }