Remove unused include in sequenced_worker_pool.h

net/ssl/ssl_platform_key_util.h

 // Copyright 2015 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 NET_SSL_SSL_PLATFORM_KEY_UTIL_H_
 #define NET_SSL_SSL_PLATFORM_KEY_UTIL_H_
 
 #include <stddef.h>
 
 #include "base/memory/ref_counted.h"
+#include "base/single_thread_task_runner.h"
 #include "net/base/net_export.h"
 #include "net/ssl/ssl_private_key.h"
 
-namespace base {
-class SingleThreadTaskRunner;
-}
-
 namespace net {
 
 class X509Certificate;
 
 // Returns a task runner to serialize all private key operations on a single
 // background thread to avoid problems with buggy smartcards. Its underlying
 // Thread is non-joinable and as such provides
 // TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN semantics.
 scoped_refptr<base::SingleThreadTaskRunner> GetSSLPlatformKeyTaskRunner();
 
 // Determines the key type and maximum signature length of |certificate|'s
 // public key.
 NET_EXPORT_PRIVATE bool GetClientCertInfo(const X509Certificate* certificate,
                                           SSLPrivateKey::Type* out_type,
                                           size_t* out_max_length);
 
 }  // namespace net
 
 #endif  // NET_SSL_SSL_PLATFORM_KEY_UTIL_H_