Fix 'enumeration not handled in switch' error on Win-Clang bots

ipc/attachment_broker_unprivileged_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_unprivileged_win.h"
 
 #include "base/process/process.h"
 #include "ipc/attachment_broker_messages.h"
 #include "ipc/brokerable_attachment.h"
 #include "ipc/handle_attachment_win.h"
@@ skipping 10 matching lines @@
     base::ProcessId destination_process) {
   switch (attachment->GetBrokerableType()) {
     case BrokerableAttachment::WIN_HANDLE: {
       const internal::HandleAttachmentWin* handle_attachment =
           static_cast<const internal::HandleAttachmentWin*>(attachment);
       internal::HandleAttachmentWin::WireFormat format =
           handle_attachment->GetWireFormat(destination_process);
       return get_sender()->Send(
           new AttachmentBrokerMsg_DuplicateWinHandle(format));
     }
+    case BrokerableAttachment::MACH_PORT:
     case BrokerableAttachment::PLACEHOLDER:
       NOTREACHED();
       return false;
   }
   return false;
 }
 
 bool AttachmentBrokerUnprivilegedWin::OnMessageReceived(const Message& msg) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(AttachmentBrokerUnprivilegedWin, msg)
     IPC_MESSAGE_HANDLER(AttachmentBrokerMsg_WinHandleHasBeenDuplicated,
                         OnWinHandleHasBeenDuplicated)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   return handled;
 }
 
 void AttachmentBrokerUnprivilegedWin::OnWinHandleHasBeenDuplicated(
     const IPC::internal::HandleAttachmentWin::WireFormat& wire_format) {
   // The IPC message was intended for a different process. Ignore it.
   if (wire_format.destination_process != base::Process::Current().Pid())
     return;
 
   scoped_refptr<BrokerableAttachment> attachment(
       new IPC::internal::HandleAttachmentWin(wire_format));
   HandleReceivedAttachment(attachment);
 }
 
 }  // namespace IPC