extensions: Cleanup class/struct fwd declarations

extensions/utility/unpacker.h

 // Copyright (c) 2012 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 EXTENSIONS_UTILITY_UNPACKER_H_
 #define EXTENSIONS_UTILITY_UNPACKER_H_
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "extensions/common/manifest.h"
 
-class SkBitmap;
-
 namespace base {
 class DictionaryValue;
 }
 
 namespace extensions {
 
 // This class unpacks an extension.  It is designed to be used in a sandboxed
 // child process.  We parse various bits of the extension, then report back to
 // the browser process, who then transcodes the pre-parsed bits and writes them
 // back out to disk for later use.
@@ skipping 82 matching lines @@
 
   // The last error message that was set.  Empty if there were no errors.
   base::string16 error_message_;
 
   DISALLOW_COPY_AND_ASSIGN(Unpacker);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_UTILITY_UNPACKER_H_