Revert Dart_PropagateError until I can track down the problems in

runtime/vm/isolate.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/isolate.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/bigint_store.h"
 #include "vm/code_index_table.h"
@@ skipping 340 matching lines @@
 
   // Read object back from the snapshot.
   SnapshotReader reader(snapshot, Isolate::Current());
   Instance& instance = Instance::Handle();
   instance ^= reader.ReadObject();
   return instance.raw();
 }
 
 
 
-RawError* Isolate::StandardRunLoop() {
+RawObject* Isolate::StandardRunLoop() {
+  ASSERT(long_jump_base() != NULL);
   ASSERT(message_notify_callback() == NULL);
   ASSERT(message_handler() != NULL);
 
   while (message_handler()->HasLivePorts()) {
     ASSERT(this == Isolate::Current());
     Zone zone(this);
     HandleScope handle_scope(this);
 
     Message* message = message_handler()->queue()->Dequeue(0);
     if (message != NULL) {
       if (message->priority() >= Message::kOOBPriority) {
         // TODO(turnidge): Out of band messages will not go through the
         // regular message handler.  Instead they will be dispatched to
         // special vm code.  Implement.
         UNIMPLEMENTED();
       }
       const Instance& msg =
           Instance::Handle(DeserializeMessage(message->data()));
       const Object& result = Object::Handle(
           DartLibraryCalls::HandleMessage(
               message->dest_port(), message->reply_port(), msg));
       delete message;
       if (result.IsError()) {
-        Error& error = Error::Handle();
-        error ^= result.raw();
-        return error.raw();
+        return result.raw();
       }
       ASSERT(result.IsNull());
     }
   }
 
   // Indicates success.
-  return Error::null();
+  return Object::null();
 }
 
 
 void Isolate::VisitObjectPointers(ObjectPointerVisitor* visitor,
                                   bool validate_frames) {
   ASSERT(visitor != NULL);
 
   // Visit objects in the object store.
   object_store()->VisitObjectPointers(visitor);
 
@@ skipping 29 matching lines @@
 }
 
 
 void Isolate::VisitWeakPersistentHandles(HandleVisitor* visitor) {
   if (api_state() != NULL) {
     api_state()->VisitWeakHandles(visitor);
   }
 }
 
 }  // namespace dart