Fix "unused variable" warnings.

base/memory/shared_memory_mac.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 <mach/mach_vm.h>
 
 #include "base/files/file_util.h"
 #include "base/files/scoped_file.h"
@@ skipping 57 matching lines @@
 }
 
 }  // namespace
 
 SharedMemoryCreateOptions::SharedMemoryCreateOptions()
     : size(0),
       executable(false),
       share_read_only(false) {}
 
 SharedMemory::SharedMemory()
-    : readonly_mapped_file_(-1),
-      mapped_size_(0),
-      memory_(NULL),
-      read_only_(false),
-      requested_size_(0) {}
+    : mapped_size_(0), memory_(NULL), read_only_(false), requested_size_(0) {}
 
 SharedMemory::SharedMemory(const SharedMemoryHandle& handle, bool read_only)
     : shm_(handle),
-      readonly_mapped_file_(-1),
       mapped_size_(0),
       memory_(NULL),
       read_only_(read_only),
       requested_size_(0) {}
 
 SharedMemory::~SharedMemory() {
   Unmap();
   Close();
 }
 
@@ skipping 117 matching lines @@
 
   if (close_self) {
     Unmap();
     Close();
   }
 
   return success;
 }
 
 }  // namespace base