Deprecate FLAGS_quic_never_write_unencrypted_data now that the unit tests all pass.

net/quic/core/quic_packet_creator.cc

Index: net/quic/core/quic_packet_creator.cc
diff --git a/net/quic/core/quic_packet_creator.cc b/net/quic/core/quic_packet_creator.cc
index ab4d32b1dd42a15f7a8c75de7e7fdc3e22b51632..847ff6ebd63872277dc7b69f8aab9286c1c67acf 100644
--- a/net/quic/core/quic_packet_creator.cc
+++ b/net/quic/core/quic_packet_creator.cc
@@ -611,7 +611,7 @@ bool QuicPacketCreator::ShouldRetransmit(const QuicFrame& frame) {
 bool QuicPacketCreator::AddFrame(const QuicFrame& frame,
                                  bool save_retransmittable_frames) {
   DVLOG(1) << "Adding frame: " << frame;
-  if (FLAGS_quic_never_write_unencrypted_data && frame.type == STREAM_FRAME &&
+  if (frame.type == STREAM_FRAME &&
       frame.stream_frame->stream_id != kCryptoStreamId &&
       packet_.encryption_level == ENCRYPTION_NONE) {
     const string error_details = "Cannot send stream data without encryption.";