Address comments on 88686a82ed8f1037bba3deacdd679fb8e717f2f6

services/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("//mojo/public/mojo_application.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 
 mojo_native_application("tracing") {
   sources = [
     "main.cc",
   ]
 
   deps = [
     ":lib",
     "//mojo/application",
   ]
 }
 
+# Library that allows the service code to be included directly into the
+# embedding shell. Used by https://manganese.googlesource.com/.
 source_set("lib") {
   sources = [
     "trace_data_sink.cc",
     "trace_data_sink.h",
     "trace_recorder_impl.cc",
     "trace_recorder_impl.h",
     "tracing_app.cc",
     "tracing_app.h",
   ]
 
   deps = [
     "//base",
     "//mojo/application",
     "//mojo/common",
     "//mojo/data_pipe_utils",
     "//mojo/public/cpp/application",
     "//mojo/public/cpp/system",
     "//mojo/services/tracing/interfaces",
   ]
 }