[Sync] Make DirectoryBackingStore's db_ private.

sync/syncable/directory_backing_store.cc

Index: sync/syncable/directory_backing_store.cc
diff --git a/sync/syncable/directory_backing_store.cc b/sync/syncable/directory_backing_store.cc
index 6bcb96ec78143fbbc76c0e406d3d509e83129f1c..d6cb0e6c157d6053f6566dd3e7b2ae9ff9e00214 100644
--- a/sync/syncable/directory_backing_store.cc
+++ b/sync/syncable/directory_backing_store.cc
@@ -206,9 +206,9 @@ DirectoryBackingStore::DirectoryBackingStore(const string& dir_name)
 
 DirectoryBackingStore::DirectoryBackingStore(const string& dir_name,
                                              sql::Connection* db)
-    : db_(db),
-      dir_name_(dir_name),
+    : dir_name_(dir_name),
       database_page_size_(IsSyncBackingDatabase32KEnabled() ? 32768 : 4096),
+      db_(db),
       needs_column_refresh_(false) {
   DCHECK(base::ThreadTaskRunnerHandle::IsSet());
 }
@@ -334,6 +334,24 @@ bool DirectoryBackingStore::SaveChanges(
   return transaction.Commit();
 }
 
+sql::Connection* DirectoryBackingStore::db() {
+  return db_.get();
+}
+
+bool DirectoryBackingStore::IsOpen() const {
+  return db_->is_open();
+}
+
+bool DirectoryBackingStore::Open(const base::FilePath& path) {
+  DCHECK(!db_->is_open());
+  return db_->Open(path);
+}
+
+bool DirectoryBackingStore::OpenInMemory() {
+  DCHECK(!db_->is_open());
+  return db_->OpenInMemory();
+}
+
 bool DirectoryBackingStore::InitializeTables() {
   int page_size = 0;
   if (IsSyncBackingDatabase32KEnabled() && GetDatabasePageSize(&page_size) &&