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

lib/date.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 <time.h>
 
 #include "vm/bootstrap_natives.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/native_entry.h"
 #include "vm/object.h"
 #include "vm/os.h"
 
 namespace dart {
 
 static int32_t kMaxAllowedSeconds = 2100000000;
 
 DEFINE_NATIVE_ENTRY(DateNatives_timeZoneName, 1) {
   GET_NATIVE_ARGUMENT(Integer, dart_seconds, arguments->At(0));
   int64_t seconds = dart_seconds.AsInt64Value();
   if (seconds < 0 || seconds > kMaxAllowedSeconds) {
     GrowableArray<const Object*> args;
     args.Add(&dart_seconds);
     Exceptions::ThrowByType(Exceptions::kIllegalArgument, args);
   }
   const char* name = OS::GetTimeZoneName(seconds);
-  const String& dart_name = String::Handle(String::New(name));
-  arguments->SetReturn(dart_name);
+  return String::New(name);
 }
 
 
 DEFINE_NATIVE_ENTRY(DateNatives_timeZoneOffsetInSeconds, 1) {
   GET_NATIVE_ARGUMENT(Integer, dart_seconds, arguments->At(0));
   int64_t seconds = dart_seconds.AsInt64Value();
   if (seconds < 0 || seconds > kMaxAllowedSeconds) {
     GrowableArray<const Object*> args;
     args.Add(&dart_seconds);
     Exceptions::ThrowByType(Exceptions::kIllegalArgument, args);
   }
   int offset = OS::GetTimeZoneOffsetInSeconds(seconds);
-  const Integer& dart_offset = Integer::Handle(Integer::New(offset));
-  arguments->SetReturn(dart_offset);
+  return Integer::New(offset);
 }
 
 
 DEFINE_NATIVE_ENTRY(DateNatives_localTimeZoneAdjustmentInSeconds, 0) {
   int adjustment = OS::GetLocalTimeZoneAdjustmentInSeconds();
-  const Integer& dart_adjustment = Integer::Handle(Integer::New(adjustment));
-  arguments->SetReturn(dart_adjustment);
+  return Integer::New(adjustment);
 }
 
 
 DEFINE_NATIVE_ENTRY(DateNatives_currentTimeMillis, 0) {
-  const Integer& time = Integer::Handle(
-      Integer::New(OS::GetCurrentTimeMillis()));
-  arguments->SetReturn(time);
+  return Integer::New(OS::GetCurrentTimeMillis());
 }
 
 }  // namespace dart