storage: Cleanup class/struct forward declarations

storage/browser/blob/blob_reader.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_READER_H_
 #define STORAGE_BROWSER_BLOB_BLOB_READER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 21 matching lines @@
 class DrainableIOBuffer;
 class IOBuffer;
 class IOBufferWithSize;
 }
 
 namespace storage {
 class BlobDataItem;
 class BlobDataHandle;
 class BlobDataSnapshot;
 class FileStreamReader;
-class FileSystemContext;
 
 // The blob reader is used to read a blob.  This can only be used in the browser
 // process, and we need to be on the IO thread.
 //  * There can only be one read happening at a time per reader.
 //  * If a status of Status::NET_ERROR is returned, that means there was an
 //    error and the net_error() variable contains the error code.
 // Use a BlobDataHandle to create an instance.
 class STORAGE_EXPORT BlobReader {
  public:
   class STORAGE_EXPORT FileStreamReaderProvider {
@@ skipping 168 matching lines @@
 
   net::CompletionCallback size_callback_;
   net::CompletionCallback read_callback_;
 
   base::WeakPtrFactory<BlobReader> weak_factory_;
   DISALLOW_COPY_AND_ASSIGN(BlobReader);
 };
 
 }  // namespace storage
 #endif  // STORAGE_BROWSER_BLOB_BLOB_READER_H_