Dart_SetReturnValue now accepts and propagates error handles.

runtime/vm/native_entry.h

 // 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.
 
 #ifndef VM_NATIVE_ENTRY_H_
 #define VM_NATIVE_ENTRY_H_
 
 #include "platform/memory_sanitizer.h"
 
 #include "vm/allocation.h"
@@ skipping 103 matching lines @@
   static const uint8_t* ResolveSymbolInLibrary(const Library& library,
                                                uword pc);
   static const uint8_t* ResolveSymbol(uword pc);
 
   static uword NativeCallWrapperEntry();
   static void NativeCallWrapper(Dart_NativeArguments args,
                                 Dart_NativeFunction func);
 
   static uword LinkNativeCallEntry();
   static void LinkNativeCall(Dart_NativeArguments args);
+ private:
+  static bool ReturnValueIsError(NativeArguments* arguments);
+  static void PropagateErrors(NativeArguments* arguments);
 };
 
 }  // namespace dart
 
 #endif  // VM_NATIVE_ENTRY_H_