Add offset support to BitstreamBuffer.

content/common/gpu/media/v4l2_slice_video_decode_accelerator.cc

Index: content/common/gpu/media/v4l2_slice_video_decode_accelerator.cc
diff --git a/content/common/gpu/media/v4l2_slice_video_decode_accelerator.cc b/content/common/gpu/media/v4l2_slice_video_decode_accelerator.cc
index f17dc6295cb4ab44e3f8be2c9a8648d048365648..49ac50bc6cccb727a0f9575f901f89635b765717 100644
--- a/content/common/gpu/media/v4l2_slice_video_decode_accelerator.cc
+++ b/content/common/gpu/media/v4l2_slice_video_decode_accelerator.cc
@@ -1190,7 +1190,8 @@ void V4L2SliceVideoDecodeAccelerator::DecodeTask(
       io_client_, io_task_runner_,
       new base::SharedMemory(bitstream_buffer.handle(), true),
       bitstream_buffer.size(), bitstream_buffer.id()));
-  if (!bitstream_record->shm->Map(bitstream_buffer.size())) {
+  if (!bitstream_record->shm->MapAt(bitstream_buffer.offset(),
+                                    bitstream_buffer.size())) {
     LOGF(ERROR) << "Could not map bitstream_buffer";
     NOTIFY_ERROR(UNREADABLE_INPUT);
     return;