Syntax and coverage checking added to Network Traffic Annotations.

net/traffic_annotation/network_traffic_annotation.h

Index: net/traffic_annotation/network_traffic_annotation.h
diff --git a/net/traffic_annotation/network_traffic_annotation.h b/net/traffic_annotation/network_traffic_annotation.h
index 989f4f348300272732063cee88ea1da2ed9c8b6f..1b074e94b85774208fbd26f8faa10f3e3c103b5f 100644
--- a/net/traffic_annotation/network_traffic_annotation.h
+++ b/net/traffic_annotation/network_traffic_annotation.h
@@ -8,7 +8,14 @@
 namespace net {
 
 // Defined type for network traffic annotation tags.
+#if defined(_DEBUG) || defined(DCHECK_ALWAYS_ON)
+struct NetworkTrafficAnnotationTag {
+  const char* const unique_id;
+  const char* const proto;
+};
+#else
 using NetworkTrafficAnnotationTag = const char* const;
+#endif
 
 // Function to convert a network traffic annotation's unique id and protobuf
 // text into a NetworkTrafficAnnotationTag.
@@ -26,11 +33,15 @@ using NetworkTrafficAnnotationTag = const char* const;
 // //tools/traffic_annotation/sample_traffic_annotation.cc.
 // TODO(crbug.com/690323): Add tools to check annotation text's format during
 // presubmit checks.
-template <size_t N1, size_t N2>
+template <unsigned N1, unsigned N2>
 constexpr NetworkTrafficAnnotationTag DefineNetworkTrafficAnnotation(
     const char (&unique_id)[N1],
     const char (&proto)[N2]) {
+#if defined(_DEBUG) || defined(DCHECK_ALWAYS_ON)
+  return NetworkTrafficAnnotationTag({unique_id, proto});
+#else
   return unique_id;
+#endif
 }
 
 }  // namespace net
@@ -39,4 +50,7 @@ constexpr NetworkTrafficAnnotationTag DefineNetworkTrafficAnnotation(
 #define NO_TRAFFIC_ANNOTATION_YET \
   net::DefineNetworkTrafficAnnotation("Undefined", "Nothing here yet.")
 
+#define MISSING_TRAFFIC_ANNOTATION     \
+  net::DefineNetworkTrafficAnnotation( \
+      "Missing", "Function called without traffic annotation.")
 #endif  // NET_TRAFFIC_ANNOTATION_NETWORK_TRAFFIC_ANNOTATION_H_