Add QuicStringPiece which is actually StringPiece.

net/quic/core/crypto/quic_decrypter.cc

 // 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.
 
 #include "net/quic/core/crypto/quic_decrypter.h"
 
 #include "crypto/hkdf.h"
 #include "net/quic/core/crypto/aes_128_gcm_12_decrypter.h"
 #include "net/quic/core/crypto/chacha20_poly1305_decrypter.h"
 #include "net/quic/core/crypto/crypto_protocol.h"
 #include "net/quic/core/crypto/null_decrypter.h"
 #include "net/quic/platform/api/quic_logging.h"
 
-using base::StringPiece;
 using std::string;
 
 namespace net {
 
 // static
 QuicDecrypter* QuicDecrypter::Create(QuicTag algorithm) {
   switch (algorithm) {
     case kAESG:
       return new Aes128Gcm12Decrypter();
     case kCC20:
       return new ChaCha20Poly1305Decrypter();
     default:
       QUIC_LOG(FATAL) << "Unsupported algorithm: " << algorithm;
       return nullptr;
   }
 }
 
 // static
-void QuicDecrypter::DiversifyPreliminaryKey(StringPiece preliminary_key,
-                                            StringPiece nonce_prefix,
+void QuicDecrypter::DiversifyPreliminaryKey(QuicStringPiece preliminary_key,
+                                            QuicStringPiece nonce_prefix,
                                             const DiversificationNonce& nonce,
                                             size_t key_size,
                                             size_t nonce_prefix_size,
                                             string* out_key,
                                             string* out_nonce_prefix) {
   crypto::HKDF hkdf(preliminary_key.as_string() + nonce_prefix.as_string(),
-                    StringPiece(nonce.data(), nonce.size()),
+                    QuicStringPiece(nonce.data(), nonce.size()),
                     "QUIC key diversification", 0, key_size, 0,
                     nonce_prefix_size, 0);
   *out_key = hkdf.server_write_key().as_string();
   *out_nonce_prefix = hkdf.server_write_iv().as_string();
 }
 
 }  // namespace net