Add pid controller test
diff --git a/binding.gyp b/binding.gyp
index 397bb1b..c6c08e2 100644
--- a/binding.gyp
+++ b/binding.gyp
@@ -654,6 +654,7 @@
         'src/core/lib/transport/mdstr_hash_table.c',
         'src/core/lib/transport/metadata.c',
         'src/core/lib/transport/metadata_batch.c',
+        'src/core/lib/transport/pid_controller.c',
         'src/core/lib/transport/static_metadata.c',
         'src/core/lib/transport/timeout_encoding.c',
         'src/core/lib/transport/transport.c',