Fix some potential Mach port leaks from mach_host_self using a new ScopedMachPort class.

base/mac/scoped_mach_port.cc

+// 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.
+
+#include "base/mac/scoped_mach_port.h"
+
+namespace base {
+namespace mac {
+
+ScopedMachPort::ScopedMachPort(mach_port_t port) : port_(port) {
+}
+
+ScopedMachPort::~ScopedMachPort() {
+  if (port_ != MACH_PORT_NULL) {
+    mach_port_deallocate(mach_task_self(), port_);
+  }
+}
+
+}  // namespace mac
+}  // namespace base