[BlobAsync] Disk support for blob storage

storage/browser/blob/blob_data_item.h

 // Copyright (c) 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.
 
 #ifndef STORAGE_BROWSER_BLOB_BLOB_DATA_ITEM_H_
 #define STORAGE_BROWSER_BLOB_BLOB_DATA_ITEM_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 45 matching lines @@
   const DataElement& data_element() const { return *item_; }
   const DataElement* data_element_ptr() const { return item_.get(); }
   DataElement* data_element_ptr() { return item_.get(); }
 
   disk_cache::Entry* disk_cache_entry() const { return disk_cache_entry_; }
   int disk_cache_stream_index() const { return disk_cache_stream_index_; }
   int disk_cache_side_stream_index() const {
     return disk_cache_side_stream_index_;
   }
 
+  const scoped_refptr<DataHandle>& data_handle() const { return data_handle_; }
+
  private:
   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);
 
   explicit BlobDataItem(std::unique_ptr<DataElement> item);
   BlobDataItem(std::unique_ptr<DataElement> item,
                const scoped_refptr<DataHandle>& data_handle);
   BlobDataItem(std::unique_ptr<DataElement> item,
                const scoped_refptr<DataHandle>& data_handle,
                disk_cache::Entry* entry,
                int disk_cache_stream_index,
                int disk_cache_side_stream_index);
   virtual ~BlobDataItem();
 
   std::unique_ptr<DataElement> item_;
   scoped_refptr<DataHandle> data_handle_;
 
   // This naked pointer is safe because the scope is protected by the DataHandle
   // instance for disk cache entries during the lifetime of this BlobDataItem.
   disk_cache::Entry* disk_cache_entry_;
   int disk_cache_stream_index_;  // For TYPE_DISK_CACHE_ENTRY.
   int disk_cache_side_stream_index_;  // For TYPE_DISK_CACHE_ENTRY.
 };
 
 STORAGE_EXPORT bool operator==(const BlobDataItem& a, const BlobDataItem& b);
 STORAGE_EXPORT bool operator!=(const BlobDataItem& a, const BlobDataItem& b);
 
 }  // namespace storage
 
 #endif  // STORAGE_BROWSER_BLOB_BLOB_DATA_ITEM_H_