Update from https://crrev.com/305340

base/mac/scoped_mach_port.h

 // Copyright (c) 2012 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.
 
 #ifndef BASE_MAC_SCOPED_MACH_PORT_H_
 #define BASE_MAC_SCOPED_MACH_PORT_H_
 
 #include <mach/mach.h>
 
 #include "base/base_export.h"
@@ skipping 13 matching lines @@
 };
 
 struct BASE_EXPORT ReceiveRightTraits {
   static mach_port_t InvalidValue() {
     return MACH_PORT_NULL;
   }
 
   static void Free(mach_port_t port);
 };
 
+struct PortSetTraits {
+  static mach_port_t InvalidValue() {
+    return MACH_PORT_NULL;
+  }
+
+  static void Free(mach_port_t port);
+};
+
 }  // namespace internal
 
 // A scoper for handling a Mach port that names a send right. Send rights are
 // reference counted, and this takes ownership of the right on construction
 // and then removes a reference to the right on destruction. If the reference
 // is the last one on the right, the right is deallocated.
 class BASE_EXPORT ScopedMachSendRight :
     public base::ScopedGeneric<mach_port_t, internal::SendRightTraits> {
  public:
   explicit ScopedMachSendRight(mach_port_t port = traits_type::InvalidValue())
       : ScopedGeneric(port) {}
 
   operator mach_port_t() const { return get(); }
 };
 
 // A scoper for handling a Mach port's receive right. There is only one
 // receive right per port. This takes ownership of the receive right on
 // construction and then destroys the right on destruction, turning all
 // outstanding send rights into dead names.
 class BASE_EXPORT ScopedMachReceiveRight :
     public base::ScopedGeneric<mach_port_t, internal::ReceiveRightTraits> {
  public:
   explicit ScopedMachReceiveRight(
       mach_port_t port = traits_type::InvalidValue()) : ScopedGeneric(port) {}
 
   operator mach_port_t() const { return get(); }
 };
 
+// A scoper for handling a Mach port set. A port set can have only one
+// reference. This takes ownership of that single reference on construction and
+// destroys the port set on destruction. Destroying a port set does not destroy
+// the receive rights that are members of the port set.
+class BASE_EXPORT ScopedMachPortSet :
+    public ScopedGeneric<mach_port_t, internal::PortSetTraits> {
+ public:
+  explicit ScopedMachPortSet(mach_port_t port = traits_type::InvalidValue())
+      : ScopedGeneric(port) {}
+
+  operator mach_port_t() const { return get(); }
+};
+
 }  // namespace mac
 }  // namespace base
 
 #endif  // BASE_MAC_SCOPED_MACH_PORT_H_