Tool added to extract network traffic annotations.

tools/traffic_annotation/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")
+
+# Works only on desktop platforms.
+assert(is_win || is_linux || is_mac)
+
+proto_library("traffic_annotation") {
+  sources = [
+    "traffic_annotation.proto",
+  ]
+  use_protobuf_full = true
+}
+
+executable("traffic_annotation_auditor") {
+  sources = [
+    "traffic_annotation_auditor.cc",
+  ]
+
+  deps = [
+    ":traffic_annotation",
+    "//base",
+    "//net:traffic_annotation_header",
+    "//third_party/protobuf:protobuf_full",
+  ]
+}