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

sync/api/attachments/attachment_id.cc

 // 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.
 
 #include "sync/api/attachments/attachment_id.h"
 
 #include "base/logging.h"
-#include "base/rand_util.h"
+#include "sync/internal_api/public/base/attachment_id_proto.h"
 #include "sync/protocol/sync.pb.h"
 
 namespace syncer {
 
 void AttachmentId::ImmutableAttachmentIdProtoTraits::InitializeWrapper(
     Wrapper* wrapper) {
   *wrapper = new sync_pb::AttachmentIdProto();
 }
 
 void AttachmentId::ImmutableAttachmentIdProtoTraits::DestroyWrapper(
@@ skipping 27 matching lines @@
 bool AttachmentId::operator!=(const AttachmentId& other) const {
   return !operator==(other);
 }
 
 bool AttachmentId::operator<(const AttachmentId& other) const {
   return proto_.Get().unique_id() < other.proto_.Get().unique_id();
 }
 
 // Static.
 AttachmentId AttachmentId::Create() {
-  // Only requirement here is that this id must be globally unique.
-  // TODO(maniscalco): Consider making this base64 encoded.
-  sync_pb::AttachmentIdProto proto;
-  proto.set_unique_id(base::RandBytesAsString(16));
+  sync_pb::AttachmentIdProto proto = CreateAttachmentIdProto();
   return AttachmentId(&proto);
 }
 
 // Static.
 AttachmentId AttachmentId::CreateFromProto(
     const sync_pb::AttachmentIdProto& proto) {
   sync_pb::AttachmentIdProto copy_of_proto(proto);
   return AttachmentId(&copy_of_proto);
 }
 
 const sync_pb::AttachmentIdProto& AttachmentId::GetProto() const {
   return proto_.Get();
 }
 
 AttachmentId::AttachmentId(sync_pb::AttachmentIdProto* proto)
     : proto_(proto) {}
 
 }  // namespace syncer