Merge pull request #9327 from yang-g/include_fix2

Add missing include for size_t

test/core/util/memory_counters.h

@@ -34,6 +34,8 @@
 #ifndef GRPC_TEST_CORE_UTIL_MEMORY_COUNTERS_H
 #define GRPC_TEST_CORE_UTIL_MEMORY_COUNTERS_H
 
+#include <stddef.h>
+
 struct grpc_memory_counters {
   size_t total_size_relative;
   size_t total_size_absolute;