Add logging for dup() failure in SharedMemoryHandle.

base/memory/shared_memory_handle_mac.cc

 // Copyright 2015 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 <mach/mach_vm.h>
 #include <stddef.h>
 #include <sys/mman.h>
 #include <unistd.h>
 
+#include "base/logging.h"
 #include "base/mac/mac_util.h"
 #include "base/mac/mach_logging.h"
 #include "base/posix/eintr_wrapper.h"
 
 namespace base {
 
 SharedMemoryHandle::SharedMemoryHandle()
     : type_(MACH), memory_object_(MACH_PORT_NULL) {}
 
 SharedMemoryHandle::SharedMemoryHandle(
@@ skipping 40 matching lines @@
   CopyRelevantData(handle);
   return *this;
 }
 
 SharedMemoryHandle SharedMemoryHandle::Duplicate() const {
   switch (type_) {
     case POSIX: {
       if (!IsValid())
         return SharedMemoryHandle();
       int duped_fd = HANDLE_EINTR(dup(file_descriptor_.fd));
-      if (duped_fd < 0)
+      if (duped_fd < 0) {
+        DPLOG(ERROR) << "dup() failed.";
         return SharedMemoryHandle();
+      }
       return SharedMemoryHandle(FileDescriptor(duped_fd, true));
     }
     case MACH: {
       if (!IsValid())
         return SharedMemoryHandle();
 
       // Increment the ref count.
       kern_return_t kr = mach_port_mod_refs(mach_task_self(), memory_object_,
                                             MACH_PORT_RIGHT_SEND, 1);
       DCHECK_EQ(kr, KERN_SUCCESS);
@@ skipping 101 matching lines @@
       break;
     case MACH:
       memory_object_ = handle.memory_object_;
       size_ = handle.size_;
       ownership_passes_to_ipc_ = handle.ownership_passes_to_ipc_;
       break;
   }
 }
 
 }  // namespace base