Tracing V2: Import support for protobuf plugin.

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 45 matching lines @@
   deps = [
     "//base",
   ]
 }
 
 # For unit testing of generated stubs.
 proto_library("proto_zero_testing_messages") {
   visibility = [ "//components/tracing/*" ]
 
   sources = [
-    "test/example_messages.proto",
+    "test/example_proto/library.proto",
+    "test/example_proto/library_internals/galaxies.proto",
+    "test/example_proto/test_messages.proto",
   ]
 
   generator_plugin_label = "tools/proto_zero_plugin:proto_zero_plugin"
   generator_plugin_suffix = ".pbzero"
   generate_cc = false
   generate_python = false
 }
 
 source_set("unit_tests") {
   testonly = true
@@ skipping 17 matching lines @@
     "//ipc",
     "//testing/gmock:gmock",
     "//testing/gtest",
   ]
 
   if (!is_android) {
     sources += [ "browser/trace_config_file_unittest.cc" ]
     deps += [ ":startup_tracing" ]
   }
 }