chrome: Cleanup class/struct forward declarations

chrome/utility/safe_browsing/mac/udif.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 CHROME_UTILITY_SAFE_BROWSING_MAC_UDIF_H_
 #define CHROME_UTILITY_SAFE_BROWSING_MAC_UDIF_H_
 
 #include <CoreFoundation/CoreFoundation.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <sys/types.h>
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/mac/scoped_cftyperef.h"
 #include "base/macros.h"
 #include "base/memory/scoped_vector.h"
 
 namespace safe_browsing {
 namespace dmg {
 
 class ReadStream;
 class UDIFBlock;
-struct UDIFBlockChunk;
 
 // UDIFParser parses a Universal Disk Image Format file, allowing access to the
 // name, types, and data of the partitions held within the file. There is no
 // canonical documentation for UDIF, and not all disk images use UDIF (though
 // the majority do). Note that this implementation only handles UDIF and SPARSE
 // image types, not SPARSEBUNDLE.
 //
 // No guarantees are made about the position of ReadStream when using an
 // instance of this class.
 //
@@ skipping 44 matching lines @@
   ScopedVector<const UDIFBlock> blocks_;  // All blocks in the UDIF image.
   uint16_t block_size_;  // The image's block size, in bytes.
 
   DISALLOW_COPY_AND_ASSIGN(UDIFParser);
 };
 
 }  // namespace dmg
 }  // namespace safe_browsing
 
 #endif  // CHROME_UTILITY_SAFE_BROWSING_MAC_UDIF_H_