Add QuicStringPiece which is actually StringPiece.

net/quic/platform/api/quic_hostname_utils.h

 // Copyright (c) 2017 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_QUIC_PLATFORM_API_QUIC_HOSTNAME_UTILS_H_
 #define NET_QUIC_PLATFORM_API_QUIC_HOSTNAME_UTILS_H_
 
 #include "base/macros.h"
 #include "net/quic/platform/api/quic_export.h"
+#include "net/quic/platform/api/quic_string_piece.h"
 #include "net/quic/platform/impl/quic_hostname_utils_impl.h"
 
 namespace net {
 
 class QuicServerId;
 
 class QUIC_EXPORT_PRIVATE QuicHostnameUtils {
  public:
   // Returns true if the sni is valid, false otherwise.
   //  (1) disallow IP addresses;
   //  (2) check that the hostname contains valid characters only; and
   //  (3) contains at least one dot.
-  static bool IsValidSNI(base::StringPiece sni);
+  static bool IsValidSNI(QuicStringPiece sni);
 
   // Convert hostname to lowercase and remove the trailing '.'.
   // WARNING: mutates |hostname| in place and returns |hostname|.
   static char* NormalizeHostname(char* hostname);
 
   // Creates a QuicServerId from a string formatted in same manner as
   // QuicServerId::ToString().
   static void StringToQuicServerId(const std::string& str, QuicServerId* out);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(QuicHostnameUtils);
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_PLATFORM_API_QUIC_HOSTNAME_UTILS_H_