Propagate more information about ValueStore errors to callers, notably an

chrome/browser/value_store/value_store_util.cc

+// Copyright 2013 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/value_store/value_store_util.h"
+
+namespace value_store_util {
+
+scoped_ptr<std::string> NewKey(const std::string& key) {
+  return make_scoped_ptr(new std::string(key));
+}
+
+scoped_ptr<std::string> NoKey() {
+  return scoped_ptr<std::string>();
+}
+
+scoped_ptr<ValueStore::Error> NoError() {
+  return scoped_ptr<ValueStore::Error>();
+}
+
+}  // namespace value_store_util