[Sync] Move snapshot cache from SBHI to PSS.

components/sync/driver/glue/sync_backend_host_impl.h

 // 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.
 
 #ifndef COMPONENTS_SYNC_DRIVER_GLUE_SYNC_BACKEND_HOST_IMPL_H_
 #define COMPONENTS_SYNC_DRIVER_GLUE_SYNC_BACKEND_HOST_IMPL_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 60 matching lines @@
   void ActivateDirectoryDataType(ModelType type,
                                  ModelSafeGroup group,
                                  ChangeProcessor* change_processor) override;
   void DeactivateDirectoryDataType(ModelType type) override;
   void ActivateNonBlockingDataType(ModelType type,
                                    std::unique_ptr<ActivationContext>) override;
   void DeactivateNonBlockingDataType(ModelType type) override;
   void EnableEncryptEverything() override;
   UserShare* GetUserShare() const override;
   Status GetDetailedStatus() override;
-  SyncCycleSnapshot GetLastCycleSnapshot() const override;
   bool HasUnsyncedItems() const override;
   bool IsNigoriEnabled() const override;
   PassphraseType GetPassphraseType() const override;
   base::Time GetExplicitPassphraseTime() const override;
   bool IsCryptographerReady(const BaseTransaction* trans) const override;
   void GetModelSafeRoutingInfo(ModelSafeRoutingInfo* out) const override;
   void FlushDirectory() const override;
   void RequestBufferedProtocolEventsAndEnableForwarding() override;
   void DisableProtocolEventForwarding() override;
   void EnableDirectoryTypeDebugInfoForwarding() override;
@@ skipping 190 matching lines @@
   // The state of the passphrase required to decrypt the bag of encryption keys
   // in the nigori node. Updated whenever a new nigori node arrives or the user
   // manually changes their passphrase state. Cached so we can synchronously
   // check it from the UI thread.
   PassphraseType cached_passphrase_type_ = PassphraseType::IMPLICIT_PASSPHRASE;
 
   // If an explicit passphrase is in use, the time at which the passphrase was
   // first set (if available).
   base::Time cached_explicit_passphrase_time_;
 
-  // UI-thread cache of the last SyncCycleSnapshot received from syncapi.
-  SyncCycleSnapshot last_snapshot_;
-
   invalidation::InvalidationService* invalidator_;
   bool invalidation_handler_registered_ = false;
 
   // Checks that we're on the same thread this was constructed on (UI thread).
   base::ThreadChecker thread_checker_;
 
   base::WeakPtrFactory<SyncBackendHostImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncBackendHostImpl);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_DRIVER_GLUE_SYNC_BACKEND_HOST_IMPL_H_