experiment with -Wimplicit-fallthrough

net/dns/dns_config_service_posix.cc

 // Copyright (c) 2012 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/dns/dns_config_service_posix.h"
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/bind.h"
@@ skipping 248 matching lines @@
   explicit ConfigReader(DnsConfigServicePosix* service)
       : service_(service), success_(false) {}
 
   virtual void DoWork() OVERRIDE {
     base::TimeTicks start_time = base::TimeTicks::Now();
     ConfigParsePosixResult result = ReadDnsConfig(&dns_config_);
     switch (result) {
       case CONFIG_PARSE_POSIX_MISSING_OPTIONS:
       case CONFIG_PARSE_POSIX_UNHANDLED_OPTIONS:
         DCHECK(dns_config_.unhandled_options);
-        // Fall through.
+        FALLTHROUGH_INTENDED;
       case CONFIG_PARSE_POSIX_OK:
         success_ = true;
         break;
       default:
         success_ = false;
         break;
     }
     UMA_HISTOGRAM_ENUMERATION("AsyncDNS.ConfigParsePosix",
                               result, CONFIG_PARSE_POSIX_MAX);
     UMA_HISTOGRAM_BOOLEAN("AsyncDNS.ConfigParseResult", success_);
@@ skipping 220 matching lines @@
   virtual void ReadNow() OVERRIDE {}
   virtual bool StartWatching() OVERRIDE { return false; }
 };
 // static
 scoped_ptr<DnsConfigService> DnsConfigService::CreateSystemService() {
   return scoped_ptr<DnsConfigService>(new StubDnsConfigService());
 }
 #endif
 
 }  // namespace net