Use the return value of vm native methods to set the return value,

lib/object.cc

 // Copyright (c) 2011, 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/bootstrap_natives.h"
 
 #include "vm/exceptions.h"
 #include "vm/native_entry.h"
 #include "vm/object.h"
 
 namespace dart {
 
 DEFINE_NATIVE_ENTRY(Object_toString, 1) {
   const Instance& instance = Instance::CheckedHandle(arguments->At(0));
   const char* c_str = instance.ToCString();
-  arguments->SetReturn(String::Handle(String::New(c_str)));
+  return String::New(c_str);
 }
 
 
 DEFINE_NATIVE_ENTRY(Object_noSuchMethod, 3) {
   const Instance& instance = Instance::CheckedHandle(arguments->At(0));
   GET_NATIVE_ARGUMENT(String, function_name, arguments->At(1));
   GET_NATIVE_ARGUMENT(Array, func_args, arguments->At(2));
   if (instance.IsNull()) {
     GrowableArray<const Object*> args;
     args.Add(&function_name);
@@ skipping 19 matching lines @@
     const int total_num_parameters =
         function.num_fixed_parameters() + function.num_optional_parameters();
     const Array& array = Array::Handle(Array::New(total_num_parameters - 1));
     // Skip receiver.
     for (int i = 1; i < total_num_parameters; i++) {
       array.SetAt(i - 1, String::Handle(function.ParameterNameAt(i)));
     }
     dart_arguments.Add(&array);
   }
   Exceptions::ThrowByType(Exceptions::kNoSuchMethod, dart_arguments);
+  return Object::null();
 }
 
 }  // namespace dart