[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>
 #include <ostream>
 #include <string>
 
 #include "base/memory/ref_counted.h"
 #include "storage/browser/storage_browser_export.h"
 #include "storage/common/data_element.h"
 
 namespace disk_cache {
 class Entry;
 }
 
 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
 // this class is to allow the resource to stick around in the snapshot even
 // after the resource was swapped in the blob (either to disk or to memory) by
 // the BlobStorageContext.
 class STORAGE_EXPORT BlobDataItem : public base::RefCounted<BlobDataItem> {
  public:
   // The DataHandle class is used to persist resources that are needed for
   // reading this BlobDataItem. This object will stay around while any reads are
@@ skipping 25 matching lines @@
   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_;
   }
 
  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,
@@ skipping 10 matching lines @@
   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_