[Sync] Make DirectoryBackingStore's db_ private.

sync/syncable/deferred_on_disk_directory_backing_store.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/syncable/deferred_on_disk_directory_backing_store.h"
 
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "base/stl_util.h"
 #include "sync/syncable/syncable-inl.h"
@@ skipping 20 matching lines @@
       snapshot.delete_journals_to_purge.empty()) {
     return true;
   }
 
   if (!db_is_on_disk_) {
     if (!base::DeleteFile(backing_filepath_, false))
       return false;
 
     // Reopen DB on disk.
     ResetAndCreateConnection();
-    if (!db_->Open(backing_filepath_) || !InitializeTables())
+    if (!Open(backing_filepath_) || !InitializeTables())
       return false;
 
     db_is_on_disk_ = true;
   }
 
   return DirectoryBackingStore::SaveChanges(snapshot);
 }
 
 DirOpenResult DeferredOnDiskDirectoryBackingStore::Load(
     Directory::MetahandlesMap* handles_map,
     JournalIndex* delete_journals,
     MetahandleSet* metahandles_to_purge,
     Directory::KernelLoadInfo* kernel_load_info) {
   // Open an in-memory database at first to create initial sync data needed by
   // Directory.
-  CHECK(!db_->is_open());
-  if (!db_->OpenInMemory())
+  CHECK(!IsOpen());
+  if (!OpenInMemory())
     return FAILED_OPEN_DATABASE;
 
   if (!InitializeTables())
     return FAILED_OPEN_DATABASE;
   if (!LoadEntries(handles_map, metahandles_to_purge))
     return FAILED_DATABASE_CORRUPT;
   if (!LoadInfo(kernel_load_info))
     return FAILED_DATABASE_CORRUPT;
 
   return OPENED;
 }
 
 }  // namespace syncable
 }  // namespace syncer