Sync: Avoid 3 passes over SyncDarta DB when loading the directory from the disk

sync/syncable/on_disk_directory_backing_store.h

Index: sync/syncable/on_disk_directory_backing_store.h
diff --git a/sync/syncable/on_disk_directory_backing_store.h b/sync/syncable/on_disk_directory_backing_store.h
index fdeda4dfd772d5183f6be61bd9c406576ad32e10..43bc74d1b1dc2d090fd45580e15ac813ba9aef9f 100644
--- a/sync/syncable/on_disk_directory_backing_store.h
+++ b/sync/syncable/on_disk_directory_backing_store.h
@@ -22,14 +22,15 @@ class SYNC_EXPORT_PRIVATE OnDiskDirectoryBackingStore
   ~OnDiskDirectoryBackingStore() override;
   DirOpenResult Load(Directory::MetahandlesMap* handles_map,
                      JournalIndex* delete_journals,
+                     MetahandleSet* metahandles_to_purge,
                      Directory::KernelLoadInfo* kernel_load_info) override;
 
   // A helper function that will make one attempt to load the directory.
   // Unlike Load(), it does not attempt to recover from failure.
-  DirOpenResult TryLoad(
-      Directory::MetahandlesMap* handles_map,
-      JournalIndex* delete_journals,
-      Directory::KernelLoadInfo* kernel_load_info);
+  DirOpenResult TryLoad(Directory::MetahandlesMap* handles_map,
+                        JournalIndex* delete_journals,
+                        MetahandleSet* metahandles_to_purge,
+                        Directory::KernelLoadInfo* kernel_load_info);
 
  protected:
   // Subclasses may override this to avoid a possible DCHECK.