MachMessageServer: don’t deal with MACH_SEND_TRAILER

util/mach/mach_message_server.cc

Index: util/mach/mach_message_server.cc
diff --git a/util/mach/mach_message_server.cc b/util/mach/mach_message_server.cc
index 5ac9f42e7091e0494d1abb693fcc6343c5be94cf..09927a7d3a08c8a4bc94a9972a9b9bdcca19b199 100644
--- a/util/mach/mach_message_server.cc
+++ b/util/mach/mach_message_server.cc
@@ -109,9 +109,11 @@ mach_msg_return_t MachMessageServer::Run(Interface* interface,
                                      : max_request_size + trailer_alloc;
 
   mach_msg_size_t max_reply_size = interface->MachMessageServerReplySize();
-  mach_msg_size_t reply_alloc = round_page(
-      (options & MACH_SEND_TRAILER) ? (max_reply_size + MAX_TRAILER_SIZE)
-                                    : max_reply_size);
+
+  // mach_msg_server() and mach_msg_server_once() would consider whether
+  // |options| contains MACH_SEND_TRAILER and include MAX_TRAILER_SIZE in this
+  // computation if it does, but that option is ineffective on OS X.
+  mach_msg_size_t reply_alloc = round_page(max_reply_size);
 
   kern_return_t kr;