DiscIO: Move scrubbing code out of ConvertToGCZ

This way, scrubbing can also be performed when converting
to other formats.

Source/Core/DiscIO/ScrubbedBlob.h

@@ -0,0 +1,37 @@
+// Copyright 2020 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include <string>
+
+#include "DiscIO/Blob.h"
+#include "DiscIO/DiscScrubber.h"
+
+namespace DiscIO
+{
+// This class wraps another BlobReader and zeroes out data that has been
+// identified by DiscScrubber as unused.
+class ScrubbedBlob : public BlobReader
+{
+public:
+  static std::unique_ptr<ScrubbedBlob> Create(const std::string& path);
+
+  BlobType GetBlobType() const override { return m_blob_reader->GetBlobType(); }
+  u64 GetRawSize() const override { return m_blob_reader->GetRawSize(); }
+  u64 GetDataSize() const override { return m_blob_reader->GetDataSize(); }
+  bool IsDataSizeAccurate() const override { return m_blob_reader->IsDataSizeAccurate(); }
+  u64 GetBlockSize() const override { return m_blob_reader->GetBlockSize(); }
+
+  bool Read(u64 offset, u64 size, u8* out_ptr) override;
+
+private:
+  ScrubbedBlob(std::unique_ptr<BlobReader> blob_reader, DiscScrubber scrubber);
+
+  std::unique_ptr<BlobReader> m_blob_reader;
+  DiscScrubber m_scrubber;
+};
+
+}  // namespace DiscIO