media: remove base::SharedMemoryHandle usage in v4l2 encoder

This replaces a use of the legacy UnalignedSharedMemory ctor
taking a SharedMemoryHandle with the current ctor taking a
PlatformSharedMemoryRegion.

Bug: 849207


Change-Id: Iea24ebdcd941cf2fa97e19cf2aeac1a18f9773d9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1697602
Commit-Queue: Matthew Cary (CET) <mattcary@chromium.org>
Reviewed-by: Ricky Liang <jcliang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681740}

media/gpu/v4l2/v4l2_jpeg_encode_accelerator.cc

@@ -71,7 +71,7 @@ V4L2JpegEncodeAccelerator::JobRecord::JobRecord(
       output_frame(output_frame),
       quality(quality),
       task_id(task_id),
-      output_shm(base::SharedMemoryHandle(), 0, true),  // dummy
+      output_shm(base::subtle::PlatformSharedMemoryRegion(), 0, true),  // dummy
       exif_shm(nullptr) {
   if (exif_buffer) {
     exif_shm.reset(new UnalignedSharedMemory(exif_buffer->TakeRegion(),