[Sync] Adding storage key concept for ModelTypeServices.

components/sync/core/processor_entity_tracker.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 COMPONENTS_SYNC_CORE_PROCESSOR_ENTITY_TRACKER_H_
 #define COMPONENTS_SYNC_CORE_PROCESSOR_ENTITY_TRACKER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 10 matching lines @@
 struct UpdateResponseData;
 
 // This class is used by the SharedModelTypeProcessor to track the state of each
 // entity with its type. It can be considered a helper class internal to the
 // processor. It manages the metadata for its entity and caches entity data
 // upon a local change until commit confirmation is received.
 class SYNC_EXPORT ProcessorEntityTracker {
  public:
   // Construct an instance representing a new locally-created item.
   static std::unique_ptr<ProcessorEntityTracker> CreateNew(
-      const std::string& client_tag,
+      const std::string& storage_key,
       const std::string& client_tag_hash,
       const std::string& id,
       base::Time creation_time);
 
   // Construct an instance representing an item loaded from storage on init.
   // This method swaps out the contents of |metadata|.
   static std::unique_ptr<ProcessorEntityTracker> CreateFromMetadata(
-      const std::string& client_tag,
+      const std::string& storage_key,
       sync_pb::EntityMetadata* metadata);
 
   ~ProcessorEntityTracker();
 
-  const std::string& client_tag() const { return client_tag_; }
+  const std::string& storage_key() const { return storage_key_; }
   const sync_pb::EntityMetadata& metadata() const { return metadata_; }
   const EntityDataPtr& commit_data() const { return commit_data_; }
 
   // Returns true if this data is out of sync with the server.
   // A commit may or may not be in progress at this time.
   bool IsUnsynced() const;
 
   // Returns true if this data is out of sync with the sync thread.
   //
   // There may or may not be a commit in progress for this item, but there's
@@ skipping 64 matching lines @@
   bool MatchesBaseData(const EntityData& data) const;
 
   // Increment sequence number in the metadata. This will also update the
   // base_specifics_hash if the entity was not already unsynced.
   void IncrementSequenceNumber();
 
  private:
   friend class ProcessorEntityTrackerTest;
 
   // The constructor swaps the data from the passed metadata.
-  ProcessorEntityTracker(const std::string& client_tag,
+  ProcessorEntityTracker(const std::string& storage_key,
                          sync_pb::EntityMetadata* metadata);
 
   // Check whether |specifics| matches the stored specifics_hash.
   bool MatchesSpecificsHash(const sync_pb::EntitySpecifics& specifics) const;
 
   // Update hash string for EntitySpecifics in the metadata.
   void UpdateSpecificsHash(const sync_pb::EntitySpecifics& specifics);
 
-  // Client tag. Should always be available.
-  std::string client_tag_;
+  // Storage key. Should always be available.
+  const std::string storage_key_;
 
   // Serializable Sync metadata.
   sync_pb::EntityMetadata metadata_;
 
   // Sync data that exists for items being committed only.
   // The data is reset once commit confirmation is received.
   EntityDataPtr commit_data_;
 
   // The sequence number of the last item sent to the sync thread.
   int64_t commit_requested_sequence_number_;
 };
 
 }  // namespace syncer_v2
 
 #endif  // COMPONENTS_SYNC_CORE_PROCESSOR_ENTITY_TRACKER_H_