ipc: Make a new class PlaceholderBrokerableAttachment.

ipc/placeholder_brokerable_attachment.cc

Index: ipc/placeholder_brokerable_attachment.cc
diff --git a/ipc/ipc_handle_win.cc b/ipc/placeholder_brokerable_attachment.cc
similarity index 54%
copy from ipc/ipc_handle_win.cc
copy to ipc/placeholder_brokerable_attachment.cc
index da3b9bb6125dba3e65d0dcbf83902ee5248a5ffe..e64e3985689a0b68b5a0eb7a70e31e5fef1cb412 100644
--- a/ipc/ipc_handle_win.cc
+++ b/ipc/placeholder_brokerable_attachment.cc
@@ -2,14 +2,13 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "ipc/ipc_handle_win.h"
+#include "ipc/placeholder_brokerable_attachment.h"
 
 namespace IPC {
 
-HandleForTransit CreateHandleForTransit(HANDLE handle) {
-  HandleForTransit hft;
-  hft.handle = handle;
-  return hft;
+BrokerableAttachment::BrokerableType
+PlaceholderBrokerableAttachment::GetBrokerableType() const {
+  return PLACEHOLDER;
 }
 
 }  // namespace IPC