CHECK validation of video/audio track inclusion for mp4 muxer.

MP4 media recorder will have video and/or audio track always.
The current code does ensure of it with CHECK due to
test where it uses incomplete sample descriptions that make
the test failed with CHECK.

The fix is to refator the tests to add CHECK on the
product code.

Bug: 331682616
Change-Id: I1539f2beff35e5b2f635af8b4ee6c3b812b2e203
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5610236
Reviewed-by: Rahul Singh <rahsin@microsoft.com>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Sunggook Chue <sunggch@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#1318143}