[BlobAsync] Disk support for blob storage

storage/browser/blob/blob_data_item.h

Index: storage/browser/blob/blob_data_item.h
diff --git a/storage/browser/blob/blob_data_item.h b/storage/browser/blob/blob_data_item.h
index 9f30030cad5d69a664f306abc2bb6e3e7662cc76..68140cc0d644095892449939bc0c09d5936fa5f5 100644
--- a/storage/browser/blob/blob_data_item.h
+++ b/storage/browser/blob/blob_data_item.h
@@ -23,6 +23,7 @@ namespace storage {
 class BlobDataBuilder;
 class BlobMemoryController;
 class BlobStorageContext;
+class DataElement;
 
 // Ref counted blob item. This class owns the backing data of the blob item. The
 // backing data is immutable, and cannot change after creation. The purpose of
@@ -68,6 +69,7 @@ class STORAGE_EXPORT BlobDataItem : public base::RefCounted<BlobDataItem> {
   friend class BlobDataBuilder;
   friend class BlobMemoryController;
   friend class BlobStorageContext;
+  friend struct BlobSlice;
   friend class base::RefCounted<BlobDataItem>;
   friend STORAGE_EXPORT void PrintTo(const BlobDataItem& x, ::std::ostream* os);