Revert of Remove IPC::BrokerableAttachment.

ipc/mach_port_attachment_mac.cc

Index: ipc/mach_port_attachment_mac.cc
diff --git a/ipc/mach_port_attachment_mac.cc b/ipc/mach_port_attachment_mac.cc
index 55a85cba7d04e48a895291909ccbb72fc6f502fb..215afa967adeb066e70e8b25784214bfa961de40 100644
--- a/ipc/mach_port_attachment_mac.cc
+++ b/ipc/mach_port_attachment_mac.cc
@@ -24,6 +24,10 @@
                                              FromWire from_wire)
     : mach_port_(mach_port), owns_mach_port_(true) {}
 
+MachPortAttachmentMac::MachPortAttachmentMac(const WireFormat& wire_format)
+    : mach_port_(static_cast<mach_port_t>(wire_format.mach_port)),
+      owns_mach_port_(true) {}
+
 MachPortAttachmentMac::~MachPortAttachmentMac() {
   if (mach_port_ != MACH_PORT_NULL && owns_mach_port_) {
     kern_return_t kr = mach_port_mod_refs(mach_task_self(), mach_port_,
@@ -33,8 +37,14 @@
   }
 }
 
-MessageAttachment::Type MachPortAttachmentMac::GetType() const {
-  return Type::MACH_PORT;
+MachPortAttachmentMac::BrokerableType MachPortAttachmentMac::GetBrokerableType()
+    const {
+  return MACH_PORT;
+}
+
+MachPortAttachmentMac::WireFormat MachPortAttachmentMac::GetWireFormat(
+    const base::ProcessId& destination) const {
+  return WireFormat(static_cast<uint32_t>(mach_port_), destination);
 }
 
 }  // namespace internal