Remove QUIC_VERSION_15 now that Chrome Stable supports QUIC_VERSION_16.

net/quic/quic_config.cc

 // 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.
 
 #include "net/quic/quic_config.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "net/quic/crypto/crypto_handshake_message.h"
@@ skipping 417 matching lines @@
 QuicConfig::QuicConfig()
     : congestion_feedback_(kCGST, PRESENCE_REQUIRED),
       connection_options_(kCOPT, PRESENCE_OPTIONAL),
       loss_detection_(kLOSS, PRESENCE_OPTIONAL),
       idle_connection_state_lifetime_seconds_(kICSL, PRESENCE_REQUIRED),
       keepalive_timeout_seconds_(kKATO, PRESENCE_OPTIONAL),
       max_streams_per_connection_(kMSPC, PRESENCE_REQUIRED),
       max_time_before_crypto_handshake_(QuicTime::Delta::Zero()),
       initial_congestion_window_(kSWND, PRESENCE_OPTIONAL),
       initial_round_trip_time_us_(kIRTT, PRESENCE_OPTIONAL),
-      // TODO(rjshade): Make this PRESENCE_REQUIRED when QUIC_VERSION_16 and
-      // QUIC_VERSION_15 are retired.
+      // TODO(rjshade): Make this PRESENCE_REQUIRED when QUIC_VERSION_16 is
+      // retired.
       initial_flow_control_window_bytes_(kIFCW, PRESENCE_OPTIONAL),
       // TODO(rjshade): Make this PRESENCE_REQUIRED when retiring
       // QUIC_VERSION_19.
       initial_stream_flow_control_window_bytes_(kSFCW, PRESENCE_OPTIONAL),
       // TODO(rjshade): Make this PRESENCE_REQUIRED when retiring
       // QUIC_VERSION_19.
       initial_session_flow_control_window_bytes_(kCFCW, PRESENCE_OPTIONAL) {
 }
 
 QuicConfig::~QuicConfig() {}
@@ skipping 269 matching lines @@
         peer_hello, hello_type, error_details);
   }
   if (error == QUIC_NO_ERROR) {
     error = connection_options_.ProcessPeerHello(
         peer_hello, hello_type, error_details);
   }
   return error;
 }
 
 }  // namespace net