[Sync] Move //sync to //components/sync.

sync/engine/syncer_util.cc

Index: sync/engine/syncer_util.cc
diff --git a/sync/engine/syncer_util.cc b/sync/engine/syncer_util.cc
deleted file mode 100644
index bb0588505f39d2ad4cbbff37bb7ac386d312a50a..0000000000000000000000000000000000000000
--- a/sync/engine/syncer_util.cc
+++ /dev/null
@@ -1,667 +0,0 @@
-// 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.
-
-#include "sync/engine/syncer_util.h"
-
-#include <stdint.h>
-
-#include <algorithm>
-#include <set>
-#include <string>
-#include <vector>
-
-#include "base/base64.h"
-#include "base/location.h"
-#include "base/metrics/histogram.h"
-#include "base/rand_util.h"
-#include "base/strings/string_number_conversions.h"
-#include "sync/engine/conflict_resolver.h"
-#include "sync/engine/syncer_proto_util.h"
-#include "sync/engine/syncer_types.h"
-#include "sync/internal_api/public/base/attachment_id_proto.h"
-#include "sync/internal_api/public/base/model_type.h"
-#include "sync/internal_api/public/base/unique_position.h"
-#include "sync/protocol/bookmark_specifics.pb.h"
-#include "sync/protocol/password_specifics.pb.h"
-#include "sync/protocol/sync.pb.h"
-#include "sync/syncable/directory.h"
-#include "sync/syncable/entry.h"
-#include "sync/syncable/model_neutral_mutable_entry.h"
-#include "sync/syncable/mutable_entry.h"
-#include "sync/syncable/syncable_changes_version.h"
-#include "sync/syncable/syncable_model_neutral_write_transaction.h"
-#include "sync/syncable/syncable_proto_util.h"
-#include "sync/syncable/syncable_read_transaction.h"
-#include "sync/syncable/syncable_util.h"
-#include "sync/syncable/syncable_write_transaction.h"
-#include "sync/util/cryptographer.h"
-#include "sync/util/time.h"
-
-namespace syncer {
-
-using syncable::CHANGES_VERSION;
-using syncable::Directory;
-using syncable::Entry;
-using syncable::GET_BY_HANDLE;
-using syncable::GET_BY_ID;
-using syncable::ID;
-using syncable::Id;
-
-syncable::Id FindLocalIdToUpdate(
-    syncable::BaseTransaction* trans,
-    const sync_pb::SyncEntity& update) {
-  // Expected entry points of this function:
-  // SyncEntity has NOT been applied to SERVER fields.
-  // SyncEntity has NOT been applied to LOCAL fields.
-  // DB has not yet been modified, no entries created for this update.
-
-  const std::string& client_id = trans->directory()->cache_guid();
-  const syncable::Id& update_id = SyncableIdFromProto(update.id_string());
-
-  if (update.has_client_defined_unique_tag() &&
-      !update.client_defined_unique_tag().empty()) {
-    // When a server sends down a client tag, the following cases can occur:
-    // 1) Client has entry for tag already, ID is server style, matches
-    // 2) Client has entry for tag already, ID is server, doesn't match.
-    // 3) Client has entry for tag already, ID is local, (never matches)
-    // 4) Client has no entry for tag
-
-    // Case 1, we don't have to do anything since the update will
-    // work just fine. Update will end up in the proper entry, via ID lookup.
-    // Case 2 - Happens very rarely due to lax enforcement of client tags
-    // on the server, if two clients commit the same tag at the same time.
-    // When this happens, we pick the lexically-least ID and ignore all other
-    // items.
-    // Case 3 - We need to replace the local ID with the server ID so that
-    // this update gets targeted at the correct local entry; we expect conflict
-    // resolution to occur.
-    // Case 4 - Perfect. Same as case 1.
-
-    syncable::Entry local_entry(trans, syncable::GET_BY_CLIENT_TAG,
-                                update.client_defined_unique_tag());
-
-    // The SyncAPI equivalent of this function will return !good if IS_DEL.
-    // The syncable version will return good even if IS_DEL.
-    // TODO(chron): Unit test the case with IS_DEL and make sure.
-    if (local_entry.good()) {
-      if (local_entry.GetId().ServerKnows()) {
-        if (local_entry.GetId() != update_id) {
-          // Case 2.
-          LOG(WARNING) << "Duplicated client tag.";
-          if (local_entry.GetId() < update_id) {
-            // Signal an error; drop this update on the floor.  Note that
-            // we don't server delete the item, because we don't allow it to
-            // exist locally at all.  So the item will remain orphaned on
-            // the server, and we won't pay attention to it.
-            return syncable::Id();
-          }
-        }
-        // Target this change to the existing local entry; later,
-        // we'll change the ID of the local entry to update_id
-        // if needed.
-        return local_entry.GetId();
-      } else {
-        // Case 3: We have a local entry with the same client tag.
-        // We should change the ID of the local entry to the server entry.
-        // This will result in an server ID with base version == 0, but that's
-        // a legal state for an item with a client tag.  By changing the ID,
-        // update will now be applied to local_entry.
-        DCHECK(0 == local_entry.GetBaseVersion() ||
-               CHANGES_VERSION == local_entry.GetBaseVersion());
-        return local_entry.GetId();
-      }
-    }
-  } else if (update.has_originator_cache_guid() &&
-      update.originator_cache_guid() == client_id) {
-    // If a commit succeeds, but the response does not come back fast enough
-    // then the syncer might assume that it was never committed.
-    // The server will track the client that sent up the original commit and
-    // return this in a get updates response. When this matches a local
-    // uncommitted item, we must mutate our local item and version to pick up
-    // the committed version of the same item whose commit response was lost.
-    // There is however still a race condition if the server has not
-    // completed the commit by the time the syncer tries to get updates
-    // again. To mitigate this, we need to have the server time out in
-    // a reasonable span, our commit batches have to be small enough
-    // to process within our HTTP response "assumed alive" time.
-
-    // We need to check if we have an entry that didn't get its server
-    // id updated correctly. The server sends down a client ID
-    // and a local (negative) id. If we have a entry by that
-    // description, we should update the ID and version to the
-    // server side ones to avoid multiple copies of the same thing.
-
-    syncable::Id client_item_id = syncable::Id::CreateFromClientString(
-        update.originator_client_item_id());
-    DCHECK(!client_item_id.ServerKnows());
-    syncable::Entry local_entry(trans, GET_BY_ID, client_item_id);
-
-    // If it exists, then our local client lost a commit response.  Use
-    // the local entry.
-    if (local_entry.good() && !local_entry.GetIsDel()) {
-      int64_t old_version = local_entry.GetBaseVersion();
-      int64_t new_version = update.version();
-      DCHECK_LE(old_version, 0);
-      DCHECK_GT(new_version, 0);
-      // Otherwise setting the base version could cause a consistency failure.
-      // An entry should never be version 0 and SYNCED.
-      DCHECK(local_entry.GetIsUnsynced());
-
-      // Just a quick sanity check.
-      DCHECK(!local_entry.GetId().ServerKnows());
-
-      DVLOG(1) << "Reuniting lost commit response IDs. server id: "
-               << update_id << " local id: " << local_entry.GetId()
-               << " new version: " << new_version;
-
-      return local_entry.GetId();
-    }
-  } else if (update.has_server_defined_unique_tag() &&
-             !update.server_defined_unique_tag().empty()) {
-    // The client creates type root folders with a local ID on demand when a
-    // progress marker for the given type is initially set.
-    // The server might also attempt to send a type root folder for the same
-    // type (during the transition period until support for root folders is
-    // removed for new client versions).
-    // TODO(stanisc): crbug.com/438313: remove this once the transition to
-    // implicit root folders on the server is done.
-    syncable::Entry local_entry(trans, syncable::GET_BY_SERVER_TAG,
-                                update.server_defined_unique_tag());
-    if (local_entry.good() && !local_entry.GetId().ServerKnows()) {
-      DCHECK(local_entry.GetId() != update_id);
-      return local_entry.GetId();
-    }
-  }
-
-  // Fallback: target an entry having the server ID, creating one if needed.
-  return update_id;
-}
-
-UpdateAttemptResponse AttemptToUpdateEntry(
-    syncable::WriteTransaction* const trans,
-    syncable::MutableEntry* const entry,
-    Cryptographer* cryptographer) {
-  CHECK(entry->good());
-  if (!entry->GetIsUnappliedUpdate())
-    return SUCCESS;  // No work to do.
-  syncable::Id id = entry->GetId();
-  const sync_pb::EntitySpecifics& specifics = entry->GetServerSpecifics();
-  ModelType type = GetModelTypeFromSpecifics(specifics);
-
-  // Only apply updates that we can decrypt. If we can't decrypt the update, it
-  // is likely because the passphrase has not arrived yet. Because the
-  // passphrase may not arrive within this GetUpdates, we can't just return
-  // conflict, else we try to perform normal conflict resolution prematurely or
-  // the syncer may get stuck. As such, we return CONFLICT_ENCRYPTION, which is
-  // treated as an unresolvable conflict. See the description in syncer_types.h.
-  // This prevents any unsynced changes from commiting and postpones conflict
-  // resolution until all data can be decrypted.
-  if (specifics.has_encrypted() &&
-      !cryptographer->CanDecrypt(specifics.encrypted())) {
-    // We can't decrypt this node yet.
-    DVLOG(1) << "Received an undecryptable "
-             << ModelTypeToString(entry->GetServerModelType())
-             << " update, returning conflict_encryption.";
-    return CONFLICT_ENCRYPTION;
-  } else if (specifics.has_password() &&
-             entry->GetUniqueServerTag().empty()) {
-    // Passwords use their own legacy encryption scheme.
-    const sync_pb::PasswordSpecifics& password = specifics.password();
-    if (!cryptographer->CanDecrypt(password.encrypted())) {
-      DVLOG(1) << "Received an undecryptable password update, returning "
-               << "conflict_encryption.";
-      return CONFLICT_ENCRYPTION;
-    }
-  }
-
-  if (!entry->GetServerIsDel()) {
-    syncable::Id new_parent = entry->GetServerParentId();
-    if (!new_parent.IsNull()) {
-      // Perform this step only if the parent is specified.
-      // The unset parent means that the implicit type root would be used.
-      Entry parent(trans, GET_BY_ID, new_parent);
-      // A note on non-directory parents:
-      // We catch most unfixable tree invariant errors at update receipt time,
-      // however we deal with this case here because we may receive the child
-      // first then the illegal parent. Instead of dealing with it twice in
-      // different ways we deal with it once here to reduce the amount of code
-      // and potential errors.
-      if (!parent.good() || parent.GetIsDel() || !parent.GetIsDir()) {
-        DVLOG(1) << "Entry has bad parent, returning conflict_hierarchy.";
-        return CONFLICT_HIERARCHY;
-      }
-      if (entry->GetParentId() != new_parent) {
-        if (!entry->GetIsDel() && !IsLegalNewParent(trans, id, new_parent)) {
-          DVLOG(1) << "Not updating item " << id
-                   << ", illegal new parent (would cause loop).";
-          return CONFLICT_HIERARCHY;
-        }
-      }
-    } else {
-      // new_parent is unset.
-      DCHECK(IsTypeWithClientGeneratedRoot(type));
-    }
-  } else if (entry->GetIsDir()) {
-    Directory::Metahandles handles;
-    trans->directory()->GetChildHandlesById(trans, id, &handles);
-    if (!handles.empty()) {
-      // If we have still-existing children, then we need to deal with
-      // them before we can process this change.
-      DVLOG(1) << "Not deleting directory; it's not empty " << *entry;
-      return CONFLICT_HIERARCHY;
-    }
-  }
-
-  if (entry->GetIsUnsynced()) {
-    DVLOG(1) << "Skipping update, returning conflict for: " << id
-             << " ; it's unsynced.";
-    return CONFLICT_SIMPLE;
-  }
-
-  if (specifics.has_encrypted()) {
-    DVLOG(2) << "Received a decryptable "
-             << ModelTypeToString(entry->GetServerModelType())
-             << " update, applying normally.";
-  } else {
-    DVLOG(2) << "Received an unencrypted "
-             << ModelTypeToString(entry->GetServerModelType())
-             << " update, applying normally.";
-  }
-
-  UpdateLocalDataFromServerData(trans, entry);
-
-  return SUCCESS;
-}
-
-std::string GetUniqueBookmarkTagFromUpdate(const sync_pb::SyncEntity& update) {
-  if (!update.has_originator_cache_guid() ||
-      !update.has_originator_client_item_id()) {
-    LOG(ERROR) << "Update is missing requirements for bookmark position."
-               << " This is a server bug.";
-    return UniquePosition::RandomSuffix();
-  }
-
-  return syncable::GenerateSyncableBookmarkHash(
-      update.originator_cache_guid(), update.originator_client_item_id());
-}
-
-UniquePosition GetUpdatePosition(const sync_pb::SyncEntity& update,
-                                 const std::string& suffix) {
-  DCHECK(UniquePosition::IsValidSuffix(suffix));
-  if (!(SyncerProtoUtil::ShouldMaintainPosition(update))) {
-    return UniquePosition::CreateInvalid();
-  } else if (update.has_unique_position()) {
-    UniquePosition proto_position =
-        UniquePosition::FromProto(update.unique_position());
-    if (proto_position.IsValid()) {
-      return proto_position;
-    }
-  }
-
-  // Now, there are two cases hit here.
-  // 1. Did not receive unique_position for this update.
-  // 2. Received unique_position, but it is invalid(ex. empty).
-  // And we will create a valid position for this two cases.
-  if (update.has_position_in_parent()) {
-    return UniquePosition::FromInt64(update.position_in_parent(), suffix);
-  } else {
-    LOG(ERROR) << "No position information in update. This is a server bug.";
-    return UniquePosition::FromInt64(0, suffix);
-  }
-}
-
-namespace {
-
-// Helper to synthesize a new-style sync_pb::EntitySpecifics for use locally,
-// when the server speaks only the old sync_pb::SyncEntity_BookmarkData-based
-// protocol.
-void UpdateBookmarkSpecifics(const std::string& singleton_tag,
-                             const std::string& url,
-                             const std::string& favicon_bytes,
-                             syncable::ModelNeutralMutableEntry* local_entry) {
-  // In the new-style protocol, the server no longer sends bookmark info for
-  // the "google_chrome" folder.  Mimic that here.
-  if (singleton_tag == "google_chrome")
-    return;
-  sync_pb::EntitySpecifics pb;
-  sync_pb::BookmarkSpecifics* bookmark = pb.mutable_bookmark();
-  if (!url.empty())
-    bookmark->set_url(url);
-  if (!favicon_bytes.empty())
-    bookmark->set_favicon(favicon_bytes);
-  local_entry->PutServerSpecifics(pb);
-}
-
-void UpdateBookmarkPositioning(
-    const sync_pb::SyncEntity& update,
-    syncable::ModelNeutralMutableEntry* local_entry) {
-  // Update our unique bookmark tag.  In many cases this will be identical to
-  // the tag we already have.  However, clients that have recently upgraded to
-  // versions that support unique positions will have incorrect tags.  See the
-  // v86 migration logic in directory_backing_store.cc for more information.
-  //
-  // Both the old and new values are unique to this element.  Applying this
-  // update will not risk the creation of conflicting unique tags.
-  std::string bookmark_tag = GetUniqueBookmarkTagFromUpdate(update);
-  if (UniquePosition::IsValidSuffix(bookmark_tag)) {
-    local_entry->PutUniqueBookmarkTag(bookmark_tag);
-  }
-
-  // Update our position.
-  UniquePosition update_pos =
-      GetUpdatePosition(update, local_entry->GetUniqueBookmarkTag());
-  if (update_pos.IsValid()) {
-    local_entry->PutServerUniquePosition(update_pos);
-  }
-}
-
-}  // namespace
-
-void UpdateServerFieldsFromUpdate(
-    syncable::ModelNeutralMutableEntry* target,
-    const sync_pb::SyncEntity& update,
-    const std::string& name) {
-  if (update.deleted()) {
-    if (target->GetServerIsDel()) {
-      // If we already think the item is server-deleted, we're done.
-      // Skipping these cases prevents our committed deletions from coming
-      // back and overriding subsequent undeletions.  For non-deleted items,
-      // the version number check has a similar effect.
-      return;
-    }
-    // Mark entry as unapplied update first to ensure journaling the deletion.
-    target->PutIsUnappliedUpdate(true);
-    // The server returns very lightweight replies for deletions, so we don't
-    // clobber a bunch of fields on delete.
-    target->PutServerIsDel(true);
-    if (!target->GetUniqueClientTag().empty()) {
-      // Items identified by the client unique tag are undeletable; when
-      // they're deleted, they go back to version 0.
-      target->PutServerVersion(0);
-    } else {
-      // Otherwise, fake a server version by bumping the local number.
-      target->PutServerVersion(
-          std::max(target->GetServerVersion(), target->GetBaseVersion()) + 1);
-    }
-    return;
-  }
-
-  DCHECK_EQ(target->GetId(), SyncableIdFromProto(update.id_string()))
-      << "ID Changing not supported here";
-  if (SyncerProtoUtil::ShouldMaintainHierarchy(update)) {
-    target->PutServerParentId(SyncableIdFromProto(update.parent_id_string()));
-  } else {
-    target->PutServerParentId(syncable::Id());
-  }
-  target->PutServerNonUniqueName(name);
-  target->PutServerVersion(update.version());
-  target->PutServerCtime(ProtoTimeToTime(update.ctime()));
-  target->PutServerMtime(ProtoTimeToTime(update.mtime()));
-  target->PutServerIsDir(IsFolder(update));
-  if (update.has_server_defined_unique_tag()) {
-    const std::string& tag = update.server_defined_unique_tag();
-    target->PutUniqueServerTag(tag);
-  }
-  if (update.has_client_defined_unique_tag()) {
-    const std::string& tag = update.client_defined_unique_tag();
-    target->PutUniqueClientTag(tag);
-  }
-  // Store the datatype-specific part as a protobuf.
-  if (update.has_specifics()) {
-    DCHECK_NE(GetModelType(update), UNSPECIFIED)
-        << "Storing unrecognized datatype in sync database.";
-    target->PutServerSpecifics(update.specifics());
-  } else if (update.has_bookmarkdata()) {
-    // Legacy protocol response for bookmark data.
-    const sync_pb::SyncEntity::BookmarkData& bookmark = update.bookmarkdata();
-    UpdateBookmarkSpecifics(update.server_defined_unique_tag(),
-                            bookmark.bookmark_url(),
-                            bookmark.bookmark_favicon(),
-                            target);
-  }
-  target->PutServerAttachmentMetadata(
-      CreateAttachmentMetadata(update.attachment_id()));
-  if (SyncerProtoUtil::ShouldMaintainPosition(update)) {
-    UpdateBookmarkPositioning(update, target);
-  }
-
-  // We only mark the entry as unapplied if its version is greater than the
-  // local data. If we're processing the update that corresponds to one of our
-  // commit we don't apply it as time differences may occur.
-  if (update.version() > target->GetBaseVersion()) {
-    target->PutIsUnappliedUpdate(true);
-  }
-  DCHECK(!update.deleted());
-  target->PutServerIsDel(false);
-}
-
-// Creates a new Entry iff no Entry exists with the given id.
-void CreateNewEntry(syncable::ModelNeutralWriteTransaction *trans,
-                    const syncable::Id& id) {
-  syncable::Entry entry(trans, GET_BY_ID, id);
-  if (!entry.good()) {
-    syncable::ModelNeutralMutableEntry new_entry(
-        trans,
-        syncable::CREATE_NEW_UPDATE_ITEM,
-        id);
-  }
-}
-
-// This function is called on an entry when we can update the user-facing data
-// from the server data.
-void UpdateLocalDataFromServerData(
-    syncable::WriteTransaction* trans,
-    syncable::MutableEntry* entry) {
-  DCHECK(!entry->GetIsUnsynced());
-  DCHECK(entry->GetIsUnappliedUpdate());
-
-  DVLOG(2) << "Updating entry : " << *entry;
-  // Start by setting the properties that determine the model_type.
-  entry->PutSpecifics(entry->GetServerSpecifics());
-  // Clear the previous server specifics now that we're applying successfully.
-  entry->PutBaseServerSpecifics(sync_pb::EntitySpecifics());
-  entry->PutIsDir(entry->GetServerIsDir());
-  // This strange dance around the IS_DEL flag avoids problems when setting
-  // the name.
-  // TODO(chron): Is this still an issue? Unit test this codepath.
-  if (entry->GetServerIsDel()) {
-    entry->PutIsDel(true);
-  } else {
-    entry->PutNonUniqueName(entry->GetServerNonUniqueName());
-    entry->PutParentId(entry->GetServerParentId());
-    entry->PutUniquePosition(entry->GetServerUniquePosition());
-    entry->PutIsDel(false);
-  }
-
-  entry->PutCtime(entry->GetServerCtime());
-  entry->PutMtime(entry->GetServerMtime());
-  entry->PutBaseVersion(entry->GetServerVersion());
-  entry->PutIsDel(entry->GetServerIsDel());
-  entry->PutIsUnappliedUpdate(false);
-  entry->PutAttachmentMetadata(entry->GetServerAttachmentMetadata());
-}
-
-VerifyCommitResult ValidateCommitEntry(syncable::Entry* entry) {
-  syncable::Id id = entry->GetId();
-  if (id == entry->GetParentId()) {
-    CHECK(id.IsRoot()) << "Non-root item is self parenting." << *entry;
-    // If the root becomes unsynced it can cause us problems.
-    LOG(ERROR) << "Root item became unsynced " << *entry;
-    return VERIFY_UNSYNCABLE;
-  }
-  if (entry->IsRoot()) {
-    LOG(ERROR) << "Permanent item became unsynced " << *entry;
-    return VERIFY_UNSYNCABLE;
-  }
-  if (entry->GetIsDel() && !entry->GetId().ServerKnows()) {
-    // Drop deleted uncommitted entries.
-    return VERIFY_UNSYNCABLE;
-  }
-  return VERIFY_OK;
-}
-
-void MarkDeletedChildrenSynced(
-    syncable::Directory* dir,
-    syncable::BaseWriteTransaction* trans,
-    std::set<syncable::Id>* deleted_folders) {
-  // There's two options here.
-  // 1. Scan deleted unsynced entries looking up their pre-delete tree for any
-  //    of the deleted folders.
-  // 2. Take each folder and do a tree walk of all entries underneath it.
-  // #2 has a lower big O cost, but writing code to limit the time spent inside
-  // the transaction during each step is simpler with 1. Changing this decision
-  // may be sensible if this code shows up in profiling.
-  if (deleted_folders->empty())
-    return;
-  Directory::Metahandles handles;
-  dir->GetUnsyncedMetaHandles(trans, &handles);
-  if (handles.empty())
-    return;
-  Directory::Metahandles::iterator it;
-  for (it = handles.begin() ; it != handles.end() ; ++it) {
-    syncable::ModelNeutralMutableEntry entry(trans, GET_BY_HANDLE, *it);
-    if (!entry.GetIsUnsynced() || !entry.GetIsDel())
-      continue;
-    syncable::Id id = entry.GetParentId();
-    while (id != trans->root_id()) {
-      if (deleted_folders->find(id) != deleted_folders->end()) {
-        // We've synced the deletion of this deleted entries parent.
-        entry.PutIsUnsynced(false);
-        break;
-      }
-      Entry parent(trans, GET_BY_ID, id);
-      if (!parent.good() || !parent.GetIsDel())
-        break;
-      id = parent.GetParentId();
-    }
-  }
-}
-
-VerifyResult VerifyNewEntry(
-    const sync_pb::SyncEntity& update,
-    syncable::Entry* target,
-    const bool deleted) {
-  if (target->good()) {
-    // Not a new update.
-    return VERIFY_UNDECIDED;
-  }
-  if (deleted) {
-    // Deletion of an item we've never seen can be ignored.
-    return VERIFY_SKIP;
-  }
-
-  return VERIFY_SUCCESS;
-}
-
-// Assumes we have an existing entry; check here for updates that break
-// consistency rules.
-VerifyResult VerifyUpdateConsistency(
-    syncable::ModelNeutralWriteTransaction* trans,
-    const sync_pb::SyncEntity& update,
-    const bool deleted,
-    const bool is_directory,
-    ModelType model_type,
-    syncable::ModelNeutralMutableEntry* target) {
-
-  CHECK(target->good());
-  const syncable::Id& update_id = SyncableIdFromProto(update.id_string());
-
-  // If the update is a delete, we don't really need to worry at this stage.
-  if (deleted)
-    return VERIFY_SUCCESS;
-
-  if (model_type == UNSPECIFIED) {
-    // This update is to an item of a datatype we don't recognize. The server
-    // shouldn't have sent it to us.  Throw it on the ground.
-    return VERIFY_SKIP;
-  }
-
-  if (target->GetServerVersion() > 0) {
-    // Then we've had an update for this entry before.
-    if (is_directory != target->GetServerIsDir() ||
-        model_type != target->GetServerModelType()) {
-      if (target->GetIsDel()) {  // If we've deleted the item, we don't care.
-        return VERIFY_SKIP;
-      } else {
-        LOG(ERROR) << "Server update doesn't agree with previous updates. ";
-        LOG(ERROR) << " Entry: " << *target;
-        LOG(ERROR) << " Update: "
-                   << SyncerProtoUtil::SyncEntityDebugString(update);
-        return VERIFY_FAIL;
-      }
-    }
-
-    if (!deleted && (target->GetId() == update_id) &&
-        (target->GetServerIsDel() ||
-         (!target->GetIsUnsynced() && target->GetIsDel() &&
-          target->GetBaseVersion() > 0))) {
-      // An undelete. The latter case in the above condition is for
-      // when the server does not give us an update following the
-      // commit of a delete, before undeleting.
-      // Undeletion is common for items that reuse the client-unique tag.
-      VerifyResult result = VerifyUndelete(trans, update, target);
-      if (VERIFY_UNDECIDED != result)
-        return result;
-    }
-  }
-  if (target->GetBaseVersion() > 0) {
-    // We've committed this update in the past.
-    if (is_directory != target->GetIsDir() ||
-        model_type != target->GetModelType()) {
-      LOG(ERROR) << "Server update doesn't agree with committed item. ";
-      LOG(ERROR) << " Entry: " << *target;
-      LOG(ERROR) << " Update: "
-                 << SyncerProtoUtil::SyncEntityDebugString(update);
-      return VERIFY_FAIL;
-    }
-    if (target->GetId() == update_id) {
-      if (target->GetServerVersion() > update.version()) {
-        LOG(WARNING) << "We've already seen a more recent version.";
-        LOG(WARNING) << " Entry: " << *target;
-        LOG(WARNING) << " Update: "
-                     << SyncerProtoUtil::SyncEntityDebugString(update);
-        return VERIFY_SKIP;
-      }
-    }
-  }
-  return VERIFY_SUCCESS;
-}
-
-// Assumes we have an existing entry; verify an update that seems to be
-// expressing an 'undelete'
-VerifyResult VerifyUndelete(syncable::ModelNeutralWriteTransaction* trans,
-                            const sync_pb::SyncEntity& update,
-                            syncable::ModelNeutralMutableEntry* target) {
-  // TODO(nick): We hit this path for items deleted items that the server
-  // tells us to re-create; only deleted items with positive base versions
-  // will hit this path.  However, it's not clear how such an undeletion
-  // would actually succeed on the server; in the protocol, a base
-  // version of 0 is required to undelete an object.  This codepath
-  // should be deprecated in favor of client-tag style undeletion
-  // (where items go to version 0 when they're deleted), or else
-  // removed entirely (if this type of undeletion is indeed impossible).
-  CHECK(target->good());
-  DVLOG(1) << "Server update is attempting undelete. " << *target
-           << "Update:" << SyncerProtoUtil::SyncEntityDebugString(update);
-  // Move the old one aside and start over.  It's too tricky to get the old one
-  // back into a state that would pass CheckTreeInvariants().
-  if (target->GetIsDel()) {
-    if (target->GetUniqueClientTag().empty())
-      LOG(WARNING) << "Doing move-aside undeletion on client-tagged item.";
-    target->PutId(trans->directory()->NextId());
-    target->PutUniqueClientTag(std::string());
-    target->PutBaseVersion(CHANGES_VERSION);
-    target->PutServerVersion(0);
-    return VERIFY_SUCCESS;
-  }
-  if (update.version() < target->GetServerVersion()) {
-    LOG(WARNING) << "Update older than current server version for "
-                 << *target << " Update:"
-                 << SyncerProtoUtil::SyncEntityDebugString(update);
-    return VERIFY_SUCCESS;  // Expected in new sync protocol.
-  }
-  return VERIFY_UNDECIDED;
-}
-
-}  // namespace syncer