Remove unused QuicDecrypter::Decrypt method and implementations.

net/quic/crypto/null_decrypter.h

Index: net/quic/crypto/null_decrypter.h
diff --git a/net/quic/crypto/null_decrypter.h b/net/quic/crypto/null_decrypter.h
index 6f232900472d178ff4128aa62cd4559d5f3b7560..db98a99576c45c45c3adc3f479be08c0929e6035 100644
--- a/net/quic/crypto/null_decrypter.h
+++ b/net/quic/crypto/null_decrypter.h
@@ -24,11 +24,6 @@ class NET_EXPORT_PRIVATE NullDecrypter : public QuicDecrypter {
   // QuicDecrypter implementation
   bool SetKey(base::StringPiece key) override;
   bool SetNoncePrefix(base::StringPiece nonce_prefix) override;
-  bool Decrypt(base::StringPiece nonce,
-               base::StringPiece associated_data,
-               base::StringPiece ciphertext,
-               unsigned char* output,
-               size_t* output_length) override;
   QuicData* DecryptPacket(QuicPacketSequenceNumber sequence_number,
                           base::StringPiece associated_data,
                           base::StringPiece ciphertext) override;