Stub AsyncTask REPR on the JVM.

Unbusts the ThreadPoolScheduler build again in the async branch.

src/vm/jvm/runtime/org/perl6/nqp/sixmodel/REPRRegistry.java

@@ -35,6 +35,7 @@
 import org.perl6.nqp.sixmodel.reprs.Semaphore;
 import org.perl6.nqp.sixmodel.reprs.ConcBlockingQueue;
 import org.perl6.nqp.sixmodel.reprs.ConditionVariable;
+import org.perl6.nqp.sixmodel.reprs.AsyncTask;
 
 public class REPRRegistry {
     private static HashMap<String, Integer> reprIdMap = new HashMap<String, Integer>();
@@ -94,5 +95,6 @@ private static void addREPR(String name, REPR REPR) {
         addREPR("Semaphore", new Semaphore());
         addREPR("ConcBlockingQueue", new ConcBlockingQueue());
         addREPR("ConditionVariable", new ConditionVariable());
+        addREPR("AsyncTask", new AsyncTask());
     }
 }

src/vm/jvm/runtime/org/perl6/nqp/sixmodel/reprs/AsyncTask.java

@@ -0,0 +1,34 @@
+package org.perl6.nqp.sixmodel.reprs;
+
+import org.perl6.nqp.runtime.ExceptionHandling;
+import org.perl6.nqp.runtime.ThreadContext;
+import org.perl6.nqp.sixmodel.REPR;
+import org.perl6.nqp.sixmodel.STable;
+import org.perl6.nqp.sixmodel.SerializationReader;
+import org.perl6.nqp.sixmodel.SixModelObject;
+import org.perl6.nqp.sixmodel.TypeObject;
+
+public class AsyncTask extends REPR {
+    public SixModelObject type_object_for(ThreadContext tc, SixModelObject HOW) {
+        STable st = new STable(this, HOW);
+        SixModelObject obj = new TypeObject();
+        obj.st = st;
+        st.WHAT = obj;
+        return st.WHAT;
+    }
+
+    public SixModelObject allocate(ThreadContext tc, STable st) {
+        AsyncTaskInstance obj = new AsyncTaskInstance();
+        obj.st = st;
+        return obj;
+    }
+
+    public SixModelObject deserialize_stub(ThreadContext tc, STable st) {
+        throw ExceptionHandling.dieInternal(tc, "Cannot deserialize an async task handle");
+    }
+
+    public void deserialize_finish(ThreadContext tc, STable st,
+            SerializationReader reader, SixModelObject obj) {
+        throw ExceptionHandling.dieInternal(tc, "Cannot deserialize an async task handle");
+    }
+}

src/vm/jvm/runtime/org/perl6/nqp/sixmodel/reprs/AsyncTaskInstance.java

@@ -0,0 +1,7 @@
+package org.perl6.nqp.sixmodel.reprs;
+
+import org.perl6.nqp.sixmodel.SixModelObject;
+
+public class AsyncTaskInstance extends SixModelObject {
+
+}