Add libvda D-Bus service.

This creates a D-Bus service which will allow libvda (go/libvda) to
establish a pipe to the mojom::VideoAcceleratorFactory interface.

CrOS changes: crosreview.com/1469082

Bug: b/123326297
Test: libvda connects and has working bindings to mojom::VideoAcceleratorFactory.
Change-Id: I8cf3298da1d22a90d182536184e4819a2c47892d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1478669
Reviewed-by: Mattias Nissler <mnissler@chromium.org>
Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
Commit-Queue: Alex Lau <alexlau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#639812}
5 files changed