sandbox: Allow access to the render node by video decoder processes.

This CL allows access to the render node unconditionally by video
decoder utility processes. This is needed so that video decoders that
serve requests for Chrome renderer processes can use minigbm to
allocate output buffers [1].

[1] https://source.chromium.org/chromium/chromium/src/+/main:media/gpu/chromeos/platform_video_frame_utils.cc;l=108-134;drc=e3267d772fb05c2fdc64180d3c71c71280dd18e7

Bug: b:195769334
Test: None
Change-Id: Id7f49661212c5778e8815b728bc51929d3de5626
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3872329


Reviewed-by: Alex Gough <ajgo@chromium.org>
Commit-Queue: Andres Calderon Jaramillo <andrescj@chromium.org>
Reviewed-by: Matthew Denton <mpdenton@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1046024}