content: Cleanup class/struct forward declarations

content/browser/indexed_db/indexed_db_callbacks.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 CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_CALLBACKS_H_
 #define CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_CALLBACKS_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 10 matching lines @@
 #include "content/common/indexed_db/indexed_db.mojom.h"
 #include "content/common/indexed_db/indexed_db_key.h"
 #include "content/common/indexed_db/indexed_db_key_path.h"
 #include "url/origin.h"
 
 namespace content {
 class IndexedDBBlobInfo;
 class IndexedDBConnection;
 class IndexedDBCursor;
 class IndexedDBDatabase;
-class IndexedDBDatabaseCallbacks;
 struct IndexedDBDataLossInfo;
 struct IndexedDBDatabaseMetadata;
 struct IndexedDBReturnValue;
 struct IndexedDBValue;
 
 class CONTENT_EXPORT IndexedDBCallbacks
     : public base::RefCounted<IndexedDBCallbacks> {
  public:
   // Simple payload responses
   IndexedDBCallbacks(IndexedDBDispatcherHost* dispatcher_host,
@@ skipping 108 matching lines @@
 
   std::unique_ptr<IOThreadHelper, BrowserThread::DeleteOnIOThread> io_helper_;
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(IndexedDBCallbacks);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_CALLBACKS_H_