Keep track of which attachments are referenced by which sync entries.

sync/syncable/entry_kernel.h

 // Copyright 2012 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_SYNCABLE_ENTRY_KERNEL_H_
 #define SYNC_SYNCABLE_ENTRY_KERNEL_H_
 
 #include <set>
 
 #include "base/time/time.h"
@@ skipping 315 matching lines @@
   }
   inline sync_pb::EntitySpecifics& mutable_ref(ProtoField field) {
     return specifics_fields[field - PROTO_FIELDS_BEGIN];
   }
   inline Id& mutable_ref(IdField field) {
     return id_fields[field - ID_FIELDS_BEGIN];
   }
   inline UniquePosition& mutable_ref(UniquePositionField field) {
     return unique_position_fields[field - UNIQUE_POSITION_FIELDS_BEGIN];
   }
+  inline sync_pb::AttachmentMetadata& mutable_ref(
+      AttachmentMetadataField field) {
+    return attachment_metadata_fields[field - ATTACHMENT_METADATA_FIELDS_BEGIN];
+  }
 
   ModelType GetModelType() const;
   ModelType GetServerModelType() const;
   bool ShouldMaintainPosition() const;
 
   // Dumps all kernel info into a DictionaryValue and returns it.
   // Transfers ownership of the DictionaryValue to the caller.
   // Note: |cryptographer| is an optional parameter for use in decrypting
   // encrypted specifics. If it is NULL or the specifics are not decryptsble,
   // they will be serialized as empty proto's.
@@ skipping 28 matching lines @@
     const EntryKernelMutation& mutation);
 
 // Caller owns the return value.
 base::ListValue* EntryKernelMutationMapToValue(
     const EntryKernelMutationMap& mutations);
 
 }  // namespace syncable
 }  // namespace syncer
 
 #endif // SYNC_SYNCABLE_ENTRY_KERNEL_H_