Delete unused HexDecode method. No behavior change.

net/quic/core/quic_utils.cc

Index: net/quic/core/quic_utils.cc
diff --git a/net/quic/core/quic_utils.cc b/net/quic/core/quic_utils.cc
index aa6dd63fd22cfdcd96e82ea78f0b1f36d8f71d27..877c1ea318e5906b7348203668163044a457a017 100644
--- a/net/quic/core/quic_utils.cc
+++ b/net/quic/core/quic_utils.cc
@@ -455,10 +455,6 @@ string QuicUtils::HexEncode(StringPiece data) {
   return ::base::HexEncode(data.data(), data.size());
 }
 
-string QuicUtils::HexDecode(const char* data, size_t length) {
-  return HexDecode(StringPiece(data, length));
-}
-
 string QuicUtils::HexDecode(StringPiece data) {
   if (data.empty())
     return "";