Used a single class for SharedMemoryHandle.

base/memory/shared_memory_handle_posix.cc

 // Copyright 2017 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_handle.h"
 
 #include <unistd.h>
 
 #include "base/logging.h"
 #include "base/posix/eintr_wrapper.h"
 
 namespace base {
 
 SharedMemoryHandle::SharedMemoryHandle() = default;
+SharedMemoryHandle::SharedMemoryHandle(const SharedMemoryHandle& handle) =
+    default;
+SharedMemoryHandle& SharedMemoryHandle::operator=(
+    const SharedMemoryHandle& handle) = default;
 
 SharedMemoryHandle::SharedMemoryHandle(
     const base::FileDescriptor& file_descriptor)
     : file_descriptor_(file_descriptor) {}
 
 // static
 SharedMemoryHandle SharedMemoryHandle::ImportHandle(int fd) {
   SharedMemoryHandle handle;
   handle.file_descriptor_.fd = fd;
   handle.file_descriptor_.auto_close = false;
@@ skipping 35 matching lines @@
 
 void SharedMemoryHandle::SetOwnershipPassesToIPC(bool ownership_passes) {
   file_descriptor_.auto_close = ownership_passes;
 }
 
 bool SharedMemoryHandle::OwnershipPassesToIPC() const {
   return file_descriptor_.auto_close;
 }
 
 }  // namespace base