content: Cleanup class/struct forward declarations

content/browser/service_worker/service_worker_context_wrapper.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_BROWSER_SERVICE_WORKER_SERVICE_WORKER_CONTEXT_WRAPPER_H_
 #define CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_CONTEXT_WRAPPER_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "content/browser/service_worker/service_worker_context_core.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/service_worker_context.h"
 
 namespace base {
 class FilePath;
-class SequencedTaskRunner;
 class SingleThreadTaskRunner;
 }
 
 namespace blink {
 enum class WebNavigationHintType;
 }
 
 namespace storage {
 class QuotaManagerProxy;
 class SpecialStoragePolicy;
@@ skipping 251 matching lines @@
 
   // Must be touched on the UI thread.
   std::map<int, int> navigation_hint_task_count_per_process_;
 
   DISALLOW_COPY_AND_ASSIGN(ServiceWorkerContextWrapper);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_CONTEXT_WRAPPER_H_