Adds CryptoHandshakeMessage::HasStringPiece method.

net/quic/core/crypto/crypto_handshake_message.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_CRYPTO_HANDSHAKE_MESSAGE_H_
 #define NET_QUIC_CRYPTO_CRYPTO_HANDSHAKE_MESSAGE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 65 matching lines @@
   // GetTaglist finds an element with the given tag containing zero or more
   // tags. If such a tag doesn't exist, it returns false. Otherwise it sets
   // |out_tags| and |out_len| to point to the array of tags and returns true.
   // The array points into the CryptoHandshakeMessage and is valid only for as
   // long as the CryptoHandshakeMessage exists and is not modified.
   QuicErrorCode GetTaglist(QuicTag tag,
                            const QuicTag** out_tags,
                            size_t* out_len) const;
 
   bool GetStringPiece(QuicTag tag, base::StringPiece* out) const;
+  bool HasStringPiece(QuicTag tag) const;
 
   // GetNthValue24 interprets the value with the given tag to be a series of
   // 24-bit, length prefixed values and it returns the subvalue with the given
   // index.
   QuicErrorCode GetNthValue24(QuicTag tag,
                               unsigned index,
                               base::StringPiece* out) const;
   QuicErrorCode GetUint32(QuicTag tag, uint32_t* out) const;
   QuicErrorCode GetUint64(QuicTag tag, uint64_t* out) const;
 
@@ skipping 34 matching lines @@
   size_t minimum_size_;
 
   // The serialized form of the handshake message. This member is constructed
   // lasily.
   mutable std::unique_ptr<QuicData> serialized_;
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_CRYPTO_CRYPTO_HANDSHAKE_MESSAGE_H_