Clean VM thread shutdown:

runtime/bin/run_vm_tests.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 <stdio.h>
 
 #include "bin/file.h"
 
 #include "vm/benchmark_test.h"
 #include "vm/dart.h"
@@ skipping 95 matching lines @@
                                        dart::bin::DartUtils::OpenFile,
                                        dart::bin::DartUtils::ReadFile,
                                        dart::bin::DartUtils::WriteFile,
                                        dart::bin::DartUtils::CloseFile,
                                        NULL);
   ASSERT(err_msg == NULL);
   // Apply the filter to all registered tests.
   TestCaseBase::RunAll();
   // Apply the filter to all registered benchmarks.
   Benchmark::RunAll(argv[0]);
+
+  err_msg = Dart::Cleanup();
+  ASSERT(err_msg == NULL);
+
   // Print a warning message if no tests or benchmarks were matched.
   if (run_matches == 0) {
     fprintf(stderr, "No tests matched: %s\n", run_filter);
     return 1;
   }
   return 0;
 }
 
 }  // namespace dart
 
 
 int main(int argc, const char** argv) {
   return dart::Main(argc, argv);
 }