sync: Finish non-blocking type encryption support

sync/engine/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_CRYPTOGRAPHER_PROVIDER_H_
-#define SYNC_ENGINE_CRYPTOGRAPHER_PROVIDER_H_
-
-#include "base/memory/scoped_ptr.h"
-#include "sync/base/sync_export.h"
-
-namespace syncer {
-
-class Cryptographer;
-class ScopedCryptographerRef;
-class ScopedCryptographerInternal;
-
-// An interface for providing clients with a ScopedCryptographerRef.
-//
-// Used to expose the syncable::Directory's cryptographer to clients that
-// would otherwise not have access to the Directory.
-class SYNC_EXPORT_PRIVATE CryptographerProvider {
- public:
-  CryptographerProvider();
-  virtual ~CryptographerProvider();
-
-  virtual bool InitScopedCryptographerRef(ScopedCryptographerRef* scoped) = 0;
-};
-
-// A concrete class representing a reference to a cryptographer.
-//
-// Access to the cryptographer is lost when this class goes out of scope.
-class SYNC_EXPORT_PRIVATE ScopedCryptographerRef {
- public:
-  ScopedCryptographerRef();
-  ~ScopedCryptographerRef();
-
-  bool Initialize(ScopedCryptographerInternal* impl);
-  bool IsValid() const;
-  Cryptographer* Get() const;
-
- private:
-  scoped_ptr<ScopedCryptographerInternal> scoped_cryptographer_internal_;
-
-  DISALLOW_COPY_AND_ASSIGN(ScopedCryptographerRef);
-};
-
-// An interface class used in the implementation of the ScopedCryptographerRef.
-//
-// We use this class to allow different implementations of
-// CryptographerProvider to implement InitScopedCryptographer in different
-// ways.  The ScopedCryptographerRef itself must be stack-allocated, so it
-// can't vary depending on which kind of CryptographerProvider is used to
-// intialize it.
-class SYNC_EXPORT_PRIVATE ScopedCryptographerInternal {
- public:
-  ScopedCryptographerInternal();
-  virtual ~ScopedCryptographerInternal();
-
-  virtual Cryptographer* Get() const = 0;
-};
-
-}  // namespace syncer
-
-#endif  // SYNC_ENGINE_CRYPTOGRAPHER_PROVIDER_H_