Revert of Revert of Make SharedMemoryHandle a class on Mac.

base/memory/shared_memory_nacl.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/memory/shared_memory.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <unistd.h>
 
 #include <limits>
 
 #include "base/logging.h"
 
 namespace base {
 
 SharedMemory::SharedMemory()
     : mapped_file_(-1),
       mapped_size_(0),
       memory_(NULL),
       read_only_(false),
       requested_size_(0) {
 }
 
-SharedMemory::SharedMemory(SharedMemoryHandle handle, bool read_only)
+SharedMemory::SharedMemory(const SharedMemoryHandle& handle, bool read_only)
     : mapped_file_(handle.fd),
       mapped_size_(0),
       memory_(NULL),
       read_only_(read_only),
       requested_size_(0) {
 }
 
-SharedMemory::SharedMemory(SharedMemoryHandle handle, bool read_only,
+SharedMemory::SharedMemory(const SharedMemoryHandle& handle,
+                           bool read_only,
                            ProcessHandle process)
     : mapped_file_(handle.fd),
       mapped_size_(0),
       memory_(NULL),
       read_only_(read_only),
       requested_size_(0) {
   NOTREACHED();
 }
 
 SharedMemory::~SharedMemory() {
@@ skipping 112 matching lines @@
   new_handle->auto_close = true;
 
   if (close_self) {
     Unmap();
     Close();
   }
   return true;
 }
 
 }  // namespace base