Create isolates in a separate thread.

runtime/vm/isolate_test.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 "platform/assert.h"
 #include "vm/globals.h"
 #include "vm/isolate.h"
 #include "vm/unit_test.h"
 
 namespace dart {
@@ skipping 55 matching lines @@
   Dart_Handle async_lib = Dart_LookupLibrary(url);
   DART_CHECK_VALID(async_lib);
   DART_CHECK_VALID(Dart_Invoke(
       async_lib, NewString("_setScheduleImmediateClosure"), 1, args));
 
 
   result = Dart_Invoke(test_lib, NewString("testMain"), 0, NULL);
   EXPECT(!Dart_IsError(result));
   // Run until all ports to isolate are closed.
   result = Dart_RunLoop();
-  EXPECT_ERROR(result, "Null callback specified for isolate creation");
+  EXPECT_ERROR(result,
+               "Isolate spawn is not supported by this Dart implementation");
   EXPECT(Dart_ErrorHasException(result));
   Dart_Handle exception_result = Dart_ErrorGetException(result);
   EXPECT_VALID(exception_result);
 }
 
 }  // namespace dart