content: Cleanup class/struct forward declarations

content/child/indexed_db/webidbfactory_impl.h

 // Copyright 2013 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_CHILD_INDEXED_DB_WEBIDBFACTORY_IMPL_H_
 #define CONTENT_CHILD_INDEXED_DB_WEBIDBFACTORY_IMPL_H_
 
 #include "base/memory/ref_counted.h"
 #include "content/common/indexed_db/indexed_db.mojom.h"
 #include "third_party/WebKit/public/platform/WebVector.h"
 #include "third_party/WebKit/public/platform/modules/indexeddb/WebIDBCallbacks.h"
 #include "third_party/WebKit/public/platform/modules/indexeddb/WebIDBDatabaseCallbacks.h"
 #include "third_party/WebKit/public/platform/modules/indexeddb/WebIDBFactory.h"
 
 namespace blink {
 class WebSecurityOrigin;
 class WebString;
 }
 
 namespace IPC {
 class SyncMessageFilter;
 }
 
 namespace content {
-class IndexedDBCallbacksImpl;
-class IndexedDBDatabaseCallbacksImpl;
 class ThreadSafeSender;
 
 class WebIDBFactoryImpl : public blink::WebIDBFactory {
  public:
   WebIDBFactoryImpl(scoped_refptr<IPC::SyncMessageFilter> sync_message_filter,
                     scoped_refptr<ThreadSafeSender> thread_safe_sender,
                     scoped_refptr<base::SingleThreadTaskRunner> io_runner);
   ~WebIDBFactoryImpl() override;
 
   // See WebIDBFactory.h for documentation on these functions.
@@ skipping 13 matching lines @@
   class IOThreadHelper;
 
   IOThreadHelper* io_helper_;
   scoped_refptr<ThreadSafeSender> thread_safe_sender_;
   scoped_refptr<base::SingleThreadTaskRunner> io_runner_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_INDEXED_DB_WEBIDBFACTORY_IMPL_H_