make base::SharedMemoryHandle a class on POSIX.

chrome/gpu/arc_gpu_video_decode_accelerator.cc

Index: chrome/gpu/arc_gpu_video_decode_accelerator.cc
diff --git a/chrome/gpu/arc_gpu_video_decode_accelerator.cc b/chrome/gpu/arc_gpu_video_decode_accelerator.cc
index 32e7ad7f38be370e4145078460769e8ee1449f6f..d0212aef014d6768ec1769fef8950d00650ab180 100644
--- a/chrome/gpu/arc_gpu_video_decode_accelerator.cc
+++ b/chrome/gpu/arc_gpu_video_decode_accelerator.cc
@@ -296,7 +296,8 @@ void ArcGpuVideoDecodeAccelerator::UseBuffer(PortType port,
       }
       CreateInputRecord(bitstream_buffer_id, index, metadata.timestamp);
       vda_->Decode(media::BitstreamBuffer(
-          bitstream_buffer_id, base::SharedMemoryHandle(dup_fd, true),
+          bitstream_buffer_id,
+          base::SharedMemoryHandle(base::FileDescriptor(dup_fd, true)),
           metadata.bytes_used, input_info->offset));
       break;
     }