[Sync] Separate purge types step from sync manager configuration.

components/sync/syncable/directory.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_SYNCABLE_DIRECTORY_H_
 #define COMPONENTS_SYNC_SYNCABLE_DIRECTORY_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 446 matching lines @@
   // sync session. |types_to_journal| must be a subset of |disabled_types|.
   // 2. Data associated with |types_to_unapply| is reset to an "unapplied"
   // state, wherein all local data is deleted and IS_UNAPPLIED is set to true.
   // This is useful when there's no benefit in discarding the currently
   // downloaded state, such as when there are cryptographer errors.
   // |types_to_unapply| must be a subset of |disabled_types|.
   // 3. All other data is purged entirely.
   // Note: "Purge" is just meant to distinguish from "deleting" entries, which
   // means something different in the syncable namespace.
   // WARNING! This can be real slow, as it iterates over all entries.
-  // WARNING! Performs synchronous I/O.
-  // Returns: true on success, false if an error was encountered.
-  virtual bool PurgeEntriesWithTypeIn(ModelTypeSet disabled_types,
-                                      ModelTypeSet types_to_journal,
-                                      ModelTypeSet types_to_unapply);
+  void PurgeEntriesWithTypeIn(ModelTypeSet disabled_types,
+                              ModelTypeSet types_to_journal,
+                              ModelTypeSet types_to_unapply);
 
   // Resets the base_versions and server_versions of all synced entities
   // associated with |type| to 1.
   // WARNING! This can be slow, as it iterates over all entries for a type.
   bool ResetVersionsForType(BaseWriteTransaction* trans, ModelType type);
 
   // Returns true iff the attachment identified by |attachment_id_proto| is
   // linked to an entry.
   //
   // An attachment linked to a deleted entry is still considered linked if the
@@ skipping 181 matching lines @@
 
   base::WeakPtrFactory<Directory> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Directory);
 };
 
 }  // namespace syncable
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_SYNCABLE_DIRECTORY_H_