Set VMTag from stubs when transitioning between Dart and Native

runtime/vm/isolate.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/isolate.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/json.h"
 #include "lib/mirrors.h"
@@ skipping 100 matching lines @@
 }
 
 
 bool IsolateMessageHandler::HandleMessage(Message* message) {
   StartIsolateScope start_scope(isolate_);
   StackZone zone(isolate_);
   HandleScope handle_scope(isolate_);
   // TODO(turnidge): Rework collection total dart execution.  This can
   // overcount when other things (gc, compilation) are active.
   TIMERSCOPE(isolate_, time_dart_execution);
-  VMTagScope tagScope(isolate_, VMTag::kScriptTagId);
 
   // If the message is in band we lookup the receive port to dispatch to.  If
   // the receive port is closed, we drop the message without deserializing it.
   Object& receive_port = Object::Handle();
   if (!message->IsOOB()) {
     receive_port = DartLibraryCalls::LookupReceivePort(message->dest_port());
     if (receive_port.IsError()) {
       return ProcessUnhandledException(Object::null_instance(),
                                        Error::Cast(receive_port));
     }
@@ skipping 956 matching lines @@
   return func.raw();
 }
 
 
 void IsolateSpawnState::Cleanup() {
   SwitchIsolateScope switch_scope(isolate());
   Dart::ShutdownIsolate();
 }
 
 }  // namespace dart