[Storage] Blob Storage Refactoring pt 1

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>
+
+#include "base/memory/ref_counted.h"
+#include "base/supports_user_data.h"
+#include "storage/browser/blob/blob_data_item.h"
+#include "storage/browser/storage_browser_export.h"
+
+namespace storage {
+class BlobDataBuilder;
+
+// Snapshot of a Blob. This snapshot holds a refcount of the current
+// blob item resources so the backing storage for these items will stick
+// around for the lifetime of this object. (The data represented by a blob is
+// immutable, but the backing store can change). Keeping this object alive
+// guarantees that the resources stay alive, but it does not guarentee that
+// the blob stays alive.  Use the BlobDataHandle to keep a blob alive.
+// This class must be deleted on the IO thread.
+class STORAGE_EXPORT BlobDataSnapshot : public base::SupportsUserData::Data {
+ public:
+  BlobDataSnapshot(const BlobDataSnapshot& other);
+  ~BlobDataSnapshot() override;
+
+  const std::vector<scoped_refptr<BlobDataItem>>& items() const {
+    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;
+  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_;
+};
+
+}  // namespace storage
+#endif  // STORAGE_BROWSER_BLOB_BLOB_DATA_SNAPSHOT_H_