Modify TlsFetchKeyMaterials comments.
diff --git a/src/core/lib/security/security_connector/tls/tls_security_connector.h b/src/core/lib/security/security_connector/tls/tls_security_connector.h
index 515f1a7..4ac831f 100644
--- a/src/core/lib/security/security_connector/tls/tls_security_connector.h
+++ b/src/core/lib/security/security_connector/tls/tls_security_connector.h
@@ -159,8 +159,9 @@
* called by a server, then the method return an error code.
*
* The arguments are detailed below:
- * - key_materials_config: a key material config that will be populated by the
- * method on success; the caller should not pass in nullptr.
+ * - key_materials_config: a key materials config that will be populated by the
+ * method on success; the caller should not pass in nullptr. Any data held by
+ * the config will be overwritten.
* - options: the TLS credentials options whose credential reloading config
* will be used to populate |key_materials_config|.
* - is_server: true denotes that this method is called by a server, and
