add trace context proto
diff --git a/build.yaml b/build.yaml
index 9b182d2..8599d6b 100644
--- a/build.yaml
+++ b/build.yaml
@@ -24,6 +24,7 @@
   - src/core/ext/census/census_interface.h
   - src/core/ext/census/census_rpc_stats.h
   - src/core/ext/census/gen/census.pb.h
+  - src/core/ext/census/gen/trace_context.pb.h
   - src/core/ext/census/grpc_filter.h
   - src/core/ext/census/mlog.h
   - src/core/ext/census/resource.h
@@ -32,6 +33,7 @@
   - src/core/ext/census/base_resources.c
   - src/core/ext/census/context.c
   - src/core/ext/census/gen/census.pb.c
+  - src/core/ext/census/gen/trace_context.pb.c
   - src/core/ext/census/grpc_context.c
   - src/core/ext/census/grpc_filter.c
   - src/core/ext/census/grpc_plugin.c