Protobuf for Traffic Annotation and first use by a URLFetcher.

net/BUILD.gn

Index: net/BUILD.gn
diff --git a/net/BUILD.gn b/net/BUILD.gn
index 8dfc8bf1742b8b5270813e0d164f996b30817c8a..5f1d3a682d61f05c835ae62ef7576db7c816178a 100644
--- a/net/BUILD.gn
+++ b/net/BUILD.gn
@@ -1646,6 +1646,7 @@ component("net") {
       "websockets/websocket_stream.h",
     ]
     deps += [
+      ":traffic_annotation",
       "//base/third_party/dynamic_annotations",
       "//sdch",
       "//third_party/zlib",
@@ -2978,6 +2979,13 @@ source_set("simple_quic_tools") {
   ]
 }
 
+source_set("traffic_annotation") {
+  sources = [
+    "net/traffic_annotation/network_traffic_annotation.h",
+  ]
+  deps = []
+}
+
 if (!is_ios) {
   executable("quic_client") {
     sources = [