experiment with -Wimplicit-fallthrough

ppapi/proxy/serialized_handle.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 "ppapi/proxy/serialized_handle.h"
 
 #include "base/memory/shared_memory.h"
 #include "base/pickle.h"
 #include "base/platform_file.h"
 #include "build/build_config.h"
@@ skipping 118 matching lines @@
       break;
     }
     case FILE: {
       int open_flags = 0;
       PP_Resource file_io = 0;
       if (!iter->ReadInt(&open_flags) || !iter->ReadInt(&file_io))
         return false;
       hdr->open_flags = open_flags;
       hdr->file_io = file_io;
       valid_type = true;
+      break;
     }
     case SOCKET:
     case CHANNEL_HANDLE:
     case INVALID:
       valid_type = true;
       break;
     // No default so the compiler will warn us if a new type is added.
   }
   if (valid_type)
     hdr->type = Type(type);
   return valid_type;
 }
 
 }  // namespace proxy
 }  // namespace ppapi