content: Cleanup class/struct forward declarations

content/public/test/test_file_error_injector.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_PUBLIC_TEST_TEST_FILE_ERROR_INJECTOR_H_
 #define CONTENT_PUBLIC_TEST_TEST_FILE_ERROR_INJECTOR_H_
 
 #include <stddef.h>
 
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/ref_counted.h"
 #include "content/public/browser/download_interrupt_reasons.h"
 #include "url/gurl.h"
 
 namespace content {
 
-class DownloadId;
 class DownloadFileWithErrorFactory;
 class DownloadManager;
 class DownloadManagerImpl;
 
 // Test helper for injecting errors into download file operations.  All errors
 // for a download must be injected before it starts.  This class needs to be
 // |RefCountedThreadSafe| because the implementation is referenced by other
 // classes that live past the time when the user is nominally done with it.
 //
 // Once created, an error injected via InjectError() will cause any
@@ skipping 90 matching lines @@
 
   // The download manager we set the factory on.
   DownloadManagerImpl* download_manager_ = nullptr;
 
   DISALLOW_COPY_AND_ASSIGN(TestFileErrorInjector);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_TEST_TEST_FILE_ERROR_INJECTOR_H_