content: Cleanup class/struct forward declarations

content/child/blob_storage/webblobregistry_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_BLOB_STORAGE_WEBBLOBREGISTRY_IMPL_H_
 #define CONTENT_CHILD_BLOB_STORAGE_WEBBLOBREGISTRY_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/memory/ref_counted.h"
 #include "base/single_thread_task_runner.h"
 #include "storage/common/data_element.h"
 #include "third_party/WebKit/public/platform/WebBlobRegistry.h"
 
 namespace blink {
 class WebThreadSafeData;
 }  // namespace blink
 
-namespace storage {
-class DataElement;
-}
-
 namespace content {
 class BlobConsolidation;
 class ThreadSafeSender;
 
 class WebBlobRegistryImpl : public blink::WebBlobRegistry {
  public:
   WebBlobRegistryImpl(scoped_refptr<base::SingleThreadTaskRunner> io_runner,
                       scoped_refptr<base::SingleThreadTaskRunner> main_runner,
                       scoped_refptr<ThreadSafeSender> sender);
   ~WebBlobRegistryImpl() override;
@@ skipping 61 matching lines @@
   };
 
   scoped_refptr<base::SingleThreadTaskRunner> io_runner_;
   scoped_refptr<base::SingleThreadTaskRunner> main_runner_;
   scoped_refptr<ThreadSafeSender> sender_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_BLOB_STORAGE_WEBBLOBREGISTRY_IMPL_H_