Syntax and coverage checking added to Network Traffic Annotations.

net/traffic_annotation/network_traffic_annotation.h

 // Copyright 2017 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.
 
 #ifndef NET_TRAFFIC_ANNOTATION_NETWORK_TRAFFIC_ANNOTATION_H_
 #define NET_TRAFFIC_ANNOTATION_NETWORK_TRAFFIC_ANNOTATION_H_
 
 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.
 //
 // This function serves as a tag that can be discovered and extracted via
 // clang tools. This allows reviewing all network traffic that is generated
 // and annotated by Chrome.
 //
 // |unique_id| should be a string that uniquely identifies this annotation
 // across all of Chromium source code.
 // |proto| is a text-encoded NetworkTrafficAnnotation protobuf (see
 // tools/traffic_annotation/traffic_annotation.proto)
 //
 // An empty and a sample template for the text-encoded protobuf can be found in
 // //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
 
 // Placeholder for unannotated usages.
 #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_