Revert of Remove IPC::BrokerableAttachment.

ipc/mach_port_mac.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/mach_port_mac.h"
 
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/strings/string_number_conversions.h"
 #include "ipc/mach_port_attachment_mac.h"
@@ skipping 16 matching lines @@
 
 // static
 bool ParamTraits<MachPortMac>::Read(const base::Pickle* m,
                                     base::PickleIterator* iter,
                                     param_type* r) {
   scoped_refptr<base::Pickle::Attachment> base_attachment;
   if (!m->ReadAttachment(iter, &base_attachment))
     return false;
   MessageAttachment* attachment =
       static_cast<MessageAttachment*>(base_attachment.get());
-  if (attachment->GetType() != MessageAttachment::Type::MACH_PORT)
+  if (attachment->GetType() != MessageAttachment::TYPE_BROKERABLE_ATTACHMENT)
     return false;
+  BrokerableAttachment* brokerable_attachment =
+      static_cast<BrokerableAttachment*>(attachment);
+  if (brokerable_attachment->GetBrokerableType() !=
+      BrokerableAttachment::MACH_PORT) {
+    return false;
+  }
   IPC::internal::MachPortAttachmentMac* mach_port_attachment =
-      static_cast<IPC::internal::MachPortAttachmentMac*>(attachment);
+      static_cast<IPC::internal::MachPortAttachmentMac*>(brokerable_attachment);
   r->set_mach_port(mach_port_attachment->get_mach_port());
   mach_port_attachment->reset_mach_port_ownership();
   return true;
 }
 
 // static
 void ParamTraits<MachPortMac>::Log(const param_type& p, std::string* l) {
   l->append(base::StringPrintf("mach port: 0x%X", p.get_mach_port()));
 }
 
 }  // namespace IPC