Don't cleanup thread list mutex until VM shutdown is clean

runtime/vm/dart.cc

 // Copyright (c) 2013, 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/dart.h"
 
 #include "vm/code_observers.h"
 #include "vm/cpu.h"
 #include "vm/dart_api_state.h"
 #include "vm/dart_entry.h"
@@ skipping 238 matching lines @@
     // Set the VM isolate as current isolate.
     Thread::EnsureInit();
     Thread::EnterIsolate(vm_isolate_);
 
     ShutdownIsolate();
     vm_isolate_ = NULL;
     ASSERT(Isolate::IsolateListLength() == 0);
 
     TargetCPUFeatures::Cleanup();
     StoreBuffer::ShutDown();
+
+    Thread::Shutdown();
   } else {
     // Shutdown the service isolate.
     ServiceIsolate::Shutdown();
   }
 
   CodeObservers::DeleteAll();
   Timeline::Shutdown();
   Metric::Cleanup();
 
-  Thread::Shutdown();
-
   return NULL;
 }
 
 
 Isolate* Dart::CreateIsolate(const char* name_prefix,
                              const Dart_IsolateFlags& api_flags) {
   // Create a new isolate.
   Isolate* isolate = Isolate::Init(name_prefix, api_flags);
   return isolate;
 }
@@ skipping 141 matching lines @@
   return predefined_handles_->handles_.IsValidScopedHandle(address);
 }
 
 
 bool Dart::IsReadOnlyApiHandle(Dart_Handle handle) {
   ASSERT(predefined_handles_ != NULL);
   return predefined_handles_->api_handles_.IsValidHandle(handle);
 }
 
 }  // namespace dart