Shutdown the sandbox MessageServer before deleting it.

sandbox/mac/xpc_message_server.cc

Index: sandbox/mac/xpc_message_server.cc
diff --git a/sandbox/mac/xpc_message_server.cc b/sandbox/mac/xpc_message_server.cc
index d811e5d5c451d54391142d2cb868be0caa7d4cc3..13753101edebe670b298844fe4e26cfe574babd3 100644
--- a/sandbox/mac/xpc_message_server.cc
+++ b/sandbox/mac/xpc_message_server.cc
@@ -48,6 +48,10 @@ bool XPCMessageServer::Initialize() {
   return true;
 }
 
+void XPCMessageServer::Shutdown() {
+  dispatch_source_.reset();
+}
+
 pid_t XPCMessageServer::GetMessageSenderPID(IPCMessage request) {
   audit_token_t token;
   xpc_dictionary_get_audit_token(request.xpc, &token);