sync: Finish non-blocking type encryption support

sync/engine/directory_cryptographer_provider.h

-// 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.
-
-#ifndef SYNC_ENGINE_DIRECTORY_CRYPTOGRAPHER_PROVIDER_H_
-#define SYNC_ENGINE_DIRECTORY_CRYPTOGRAPHER_PROVIDER_H_
-
-#include "sync/engine/cryptographer_provider.h"
-
-#include "sync/syncable/syncable_read_transaction.h"
-
-namespace syncer {
-
-namespace syncable {
-class Directory;
-}
-
-// Provides access to the Directory's cryptographer through the
-// CryptographerProvider interface.
-class DirectoryCryptographerProvider : public CryptographerProvider {
- public:
-  DirectoryCryptographerProvider(syncable::Directory* dir);
-  virtual ~DirectoryCryptographerProvider();
-
-  virtual bool InitScopedCryptographerRef(
-      ScopedCryptographerRef* scoped) OVERRIDE;
-
- private:
-  syncable::Directory* dir_;
-};
-
-// An implementation detail of the DirectoryCryptographerProvider.  Contains
-// the ReadTransaction used to safely access the Cryptographer.
-class ScopedDirectoryCryptographerInternal
-    : public ScopedCryptographerInternal {
- public:
-  ScopedDirectoryCryptographerInternal(syncable::Directory* dir);
-  virtual ~ScopedDirectoryCryptographerInternal();
-
-  virtual Cryptographer* Get() const OVERRIDE;
-
- private:
-  syncable::Directory* dir_;
-  syncable::ReadTransaction trans_;
-
-  DISALLOW_COPY_AND_ASSIGN(ScopedDirectoryCryptographerInternal);
-};
-
-}  // namespace syncer
-
-#endif  // SYNC_ENGINE_DIRECTORY_CRYPTOGRAPHER_PROVIDER_H_