Revert "Revert 142517 - [Sync] Refactor sync configuration logic."

sync/syncable/directory.h

 // Copyright (c) 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_DIRECTORY_H_
 #define SYNC_SYNCABLE_DIRECTORY_H_
 #pragma once
 
 #include <set>
 #include <string>
@@ skipping 404 matching lines @@
   // should not be invoked outside of tests.
   bool FullyCheckTreeInvariants(BaseTransaction *trans);
 
   // Purges all data associated with any entries whose ModelType or
   // ServerModelType is found in |types|, from _both_ memory and disk.
   // Only  valid, "real" model types are allowed in |types| (see model_type.h
   // for definitions).  "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.
-  virtual void PurgeEntriesWithTypeIn(ModelTypeSet types);
+  // Returns: true on success, false if an error was encountered.
+  virtual bool PurgeEntriesWithTypeIn(ModelTypeSet types);
 
  private:
   // A helper that implements the logic of checking tree invariants.
   bool CheckTreeInvariants(syncable::BaseTransaction* trans,
                            const MetahandleSet& handles);
 
   // Helper to prime ids_index, parent_id_and_names_index, unsynced_metahandles
   // and unapplied_metahandles from metahandles_index.
   void InitializeIndices();
 
@@ skipping 170 matching lines @@
       report_unrecoverable_error_function_;
   bool unrecoverable_error_set_;
 
   InvariantCheckLevel invariant_check_level_;
 };
 
 }  // namespace syncable
 }  // namespace syncer
 
 #endif // SYNC_SYNCABLE_DIRECTORY_H_