storage: Cleanup class/struct forward declarations

storage/browser/blob/blob_memory_controller.h

 // Copyright 2016 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_MEMORY_CONTROLLER_H_
 #define STORAGE_BROWSER_BLOB_BLOB_MEMORY_CONTROLLER_H_
 
 #include <stdint.h>
 
 #include <list>
@@ skipping 16 matching lines @@
 #include "base/optional.h"
 #include "base/time/time.h"
 #include "storage/browser/storage_browser_export.h"
 #include "storage/common/blob_storage/blob_storage_constants.h"
 
 namespace base {
 class TaskRunner;
 }
 
 namespace storage {
-class DataElement;
 class ShareableBlobDataItem;
 class ShareableFileReference;
 
 // This class's main responsibility is deciding how blob data gets stored.
 // This encompasses:
 // * Keeping track of memory & file quota,
 // * How to transport the blob data from the renderer (DetermineStrategy),
 // * Allocating memory & file quota (ReserveMemoryQuota, ReserveFileQuota)
 // * Paging memory quota to disk when we're nearing our memory limit, and
 // * Maintaining an LRU of memory items to choose candidates to page to disk
@@ skipping 195 matching lines @@
   // another blob successfully grabs a ref, we can prevent it from adding the
   // item to the recent_item_cache_ above.
   std::unordered_set<uint64_t> items_paging_to_file_;
 
   base::WeakPtrFactory<BlobMemoryController> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BlobMemoryController);
 };
 }  // namespace storage
 #endif  // STORAGE_BROWSER_BLOB_BLOB_MEMORY_CONTROLLER_H_