[BlobAsync] Disk support for blob storage

storage/browser/blob/shareable_blob_data_item.cc

 // Copyright 2015 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 "storage/browser/blob/shareable_blob_data_item.h"
 
 #include "storage/browser/blob/blob_data_item.h"
 
 namespace storage {
 
-ShareableBlobDataItem::ShareableBlobDataItem(
-    const std::string& blob_uuid,
-    const scoped_refptr<BlobDataItem>& item)
-    : item_(item) {
+ShareableBlobDataItem::ShareableBlobDataItem(uint64_t item_id,
+                                             scoped_refptr<BlobDataItem> item)
+    : item_id_(item_id), item_(std::move(item)) {
   DCHECK_NE(item_->type(), DataElement::TYPE_BLOB);
-  referencing_blobs_.insert(blob_uuid);
 }
 
 ShareableBlobDataItem::~ShareableBlobDataItem() {
 }
 
 const scoped_refptr<BlobDataItem>& ShareableBlobDataItem::item() {
   return item_;
 }
 
 }  // namespace storage