Fix another 'enumerator not handled in switch' Win-Clang warning

ipc/attachment_broker_privileged_win.cc

 // Copyright 2015 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 "ipc/attachment_broker_privileged_win.h"
 
 #include <windows.h>
 
 #include "base/process/process.h"
 #include "ipc/attachment_broker_messages.h"
@@ skipping 16 matching lines @@
           static_cast<const internal::HandleAttachmentWin*>(attachment);
       HandleWireFormat wire_format =
           handle_attachment->GetWireFormat(destination_process);
       HandleWireFormat new_wire_format =
           DuplicateWinHandle(wire_format, base::Process::Current().Pid());
       if (new_wire_format.handle == 0)
         return false;
       RouteDuplicatedHandle(new_wire_format);
       return true;
     }
+    case BrokerableAttachment::MACH_PORT:
     case BrokerableAttachment::PLACEHOLDER:
       NOTREACHED();
       return false;
   }
   return false;
 }
 
 bool AttachmentBrokerPrivilegedWin::OnMessageReceived(const Message& msg) {
   bool handled = true;
   switch (msg.type()) {
@@ skipping 87 matching lines @@
 
 AttachmentBrokerPrivilegedWin::HandleWireFormat
 AttachmentBrokerPrivilegedWin::CopyWireFormat(
     const HandleWireFormat& wire_format,
     int handle) {
   return HandleWireFormat(handle, wire_format.destination_process,
                           wire_format.permissions, wire_format.attachment_id);
 }
 
 }  // namespace IPC