sync: Introduce CryptographerProvider interface

sync/engine/cryptographer_provider.cc

+// Copyright 2014 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 "sync/engine/cryptographer_provider.h"
+
+namespace syncer {
+
+CryptographerProvider::CryptographerProvider() {
+}
+
+CryptographerProvider::~CryptographerProvider() {
+}
+
+ScopedCryptographerRef::ScopedCryptographerRef() {
+}
+
+ScopedCryptographerRef::~ScopedCryptographerRef() {
+}
+
+bool ScopedCryptographerRef::Initialize(ScopedCryptographerImpl* impl) {
+  scoped_cryptographer_impl_.reset(impl);
+  return IsValid();
+}
+
+bool ScopedCryptographerRef::IsValid() const {
+  return !!Get();
+}
+
+Cryptographer* ScopedCryptographerRef::Get() const {
+  if (!scoped_cryptographer_impl_)
+    return NULL;
+  return scoped_cryptographer_impl_->Get();
+}
+
+ScopedCryptographerImpl::ScopedCryptographerImpl() {
+}
+
+ScopedCryptographerImpl::~ScopedCryptographerImpl() {
+}
+
+}  // namespace syncer