Allow a name to be provided to a persisting unit.

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@4316 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/presents/util/PersistingUnit.java

@@ -39,6 +39,13 @@ public abstract class PersistingUnit extends Invoker.Unit
 {
     public PersistingUnit (InvocationService.InvocationListener listener)
     {
+        this("UnknownPersistingUnit", listener);
+    }
+
+    public PersistingUnit (
+        String name, InvocationService.InvocationListener listener)
+    {
+        super(name);
         _listener = listener;
     }