Introduce the plumbing necessary to report Unrecoverable error from model safe workers.

chrome/browser/sync/engine/model_safe_worker.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/sync/engine/model_safe_worker.h"
+#include "chrome/browser/sync/util/unrecoverable_error_info.h"
 
 #include "base/json/json_writer.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/values.h"
 
 namespace browser_sync {
 
 base::DictionaryValue* ModelSafeRoutingInfoToValue(
     const ModelSafeRoutingInfo& routing_info) {
   base::DictionaryValue* dict = new base::DictionaryValue();
@@ skipping 51 matching lines @@
     default:
       NOTREACHED();
       return "INVALID";
   }
 }
 
 ModelSafeWorker::ModelSafeWorker() {}
 
 ModelSafeWorker::~ModelSafeWorker() {}
 
-void ModelSafeWorker::DoWorkAndWaitUntilDone(Callback0::Type* work) {
-  work->Run();  // For GROUP_PASSIVE, we do the work on the current thread.
+UnrecoverableErrorInfo ModelSafeWorker::DoWorkAndWaitUntilDone(
+  const WorkCallback& work) {
+  // For GROUP_PASSIVE, we do the work on the current thread.
+  return work.Run();
 }
 
 ModelSafeGroup ModelSafeWorker::GetModelSafeGroup() {
   return GROUP_PASSIVE;
 }
 
 }  // namespace browser_sync