[Storage] Blob items are now shared between blobs. Ready for disk swap.

storage/browser/blob/blob_data_snapshot.h

 // 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.
 
 #ifndef STORAGE_BROWSER_BLOB_BLOB_DATA_SNAPSHOT_H_
 #define STORAGE_BROWSER_BLOB_BLOB_DATA_SNAPSHOT_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 21 matching lines @@
     return items_;
   }
   const std::string& content_type() const { return content_type_; }
   const std::string& content_disposition() const {
     return content_disposition_;
   }
   size_t GetMemoryUsage() const;
 
  private:
   friend class BlobDataBuilder;
+  friend class BlobStorageContext;
+  BlobDataSnapshot(const std::string& uuid,
+                   const std::string& content_type,
+                   const std::string& content_disposition);
   BlobDataSnapshot(const std::string& uuid,
                    const std::string& content_type,
                    const std::string& content_disposition,
                    const std::vector<scoped_refptr<BlobDataItem>>& items);
 
   const std::string uuid_;
   const std::string content_type_;
   const std::string content_disposition_;
-  const std::vector<scoped_refptr<BlobDataItem>> items_;
+  // Non-const for constrution in BlobStorageContext
+  std::vector<scoped_refptr<BlobDataItem>> items_;
 };
 
 }  // namespace storage
 #endif  // STORAGE_BROWSER_BLOB_BLOB_DATA_SNAPSHOT_H_