Revert Dart_PropagateError until I can track down the problems in

runtime/vm/bootstrap_nocorelib.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.h"
 
 #include "include/dart_api.h"
 
 #include "vm/dart_api_impl.h"
 #include "vm/object.h"
 #include "vm/object_store.h"
 
 namespace dart {
 
 DEFINE_FLAG(bool, print_bootstrap, false, "Print the bootstrap source.");
 
 
 RawScript* Bootstrap::LoadScript() {
   UNREACHABLE();
   return Script::null();
 }
 
 
 RawScript* Bootstrap::LoadImplScript() {
   UNREACHABLE();
   return Script::null();
 }
 
 
-RawError* Bootstrap::Compile(const Library& library, const Script& script) {
+void Bootstrap::Compile(const Library& library, const Script& script) {
   UNREACHABLE();
-  return Error::null();
 }
 
 }  // namespace dart