experiment with -Wimplicit-fallthrough

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/quic_sent_packet_manager.h"
@@ skipping 44 matching lines @@
   QuicErrorCode error = msg.GetUint32(tag_, out);
   switch (error) {
     case QUIC_CRYPTO_MESSAGE_PARAMETER_NOT_FOUND:
       if (presence_ == QuicNegotiableValue::PRESENCE_REQUIRED) {
         *error_details = "Missing " + QuicUtils::TagToString(tag_);
         break;
       }
       error = QUIC_NO_ERROR;
       *out = default_value_;
 
+      FALLTHROUGH_INTENDED;
     case QUIC_NO_ERROR:
       break;
     default:
       *error_details = "Bad " + QuicUtils::TagToString(tag_);
       break;
   }
   return error;
 }
 
 QuicErrorCode QuicNegotiableUint32::ProcessClientHello(
@@ skipping 78 matching lines @@
   switch (error) {
     case QUIC_CRYPTO_MESSAGE_PARAMETER_NOT_FOUND:
       if (presence_ == PRESENCE_REQUIRED) {
         *error_details = "Missing " + QuicUtils::TagToString(tag_);
         break;
       }
       error = QUIC_NO_ERROR;
       *out_length = 1;
       *out = &default_value_;
 
+      FALLTHROUGH_INTENDED;
     case QUIC_NO_ERROR:
       break;
     default:
       *error_details = "Bad " + QuicUtils::TagToString(tag_);
       break;
   }
   return error;
 }
 
 QuicErrorCode QuicNegotiableTag::ProcessClientHello(
@@ skipping 231 matching lines @@
         server_hello, error_details);
   }
   if (error == QUIC_NO_ERROR) {
     error = initial_round_trip_time_us_.ProcessServerHello(
         server_hello, error_details);
   }
   return error;
 }
 
 }  // namespace net