Add logging for dup() failure in 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"
@@ skipping 39 matching lines @@
   int old_fd = file_descriptor_.fd;
   file_descriptor_.fd = -1;
   return old_fd;
 }
 
 SharedMemoryHandle SharedMemoryHandle::Duplicate() const {
   if (!IsValid())
     return SharedMemoryHandle();
 
   int duped_handle = HANDLE_EINTR(dup(file_descriptor_.fd));
-  if (duped_handle < 0)
+  if (duped_handle < 0) {
+    DPLOG(ERROR) << "dup() failed.";
     return SharedMemoryHandle();
+  }
   return SharedMemoryHandle(FileDescriptor(duped_handle, true));
 }
 
 void SharedMemoryHandle::SetOwnershipPassesToIPC(bool ownership_passes) {
   file_descriptor_.auto_close = ownership_passes;
 }
 
 bool SharedMemoryHandle::OwnershipPassesToIPC() const {
   return file_descriptor_.auto_close;
 }
 
 }  // namespace base