net: Update the include paths of base/string_piece.h to its new location.

net/quic/crypto/key_exchange.h

 // Copyright (c) 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 NET_QUIC_CRYPTO_KEY_EXCHANGE_H_
 #define NET_QUIC_CRYPTO_KEY_EXCHANGE_H_
 
 #include <string>
 
-#include "base/string_piece.h"
+#include "base/strings/string_piece.h"
 #include "net/base/net_export.h"
 #include "net/quic/crypto/crypto_protocol.h"
 
 namespace net {
 
 // KeyExchange is an abstract class that provides an interface to a
 // key-exchange primitive.
 class NET_EXPORT_PRIVATE KeyExchange {
  public:
   virtual ~KeyExchange() { }
@@ skipping 10 matching lines @@
   // KeyExchange exists.
   virtual base::StringPiece public_value() const = 0;
 
   // tag returns the tag value that identifies this key exchange function.
   virtual CryptoTag tag() const = 0;
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_CRYPTO_KEY_EXCHANGE_H_