Properly handle fallback aspect ratio for videos
A <video> element with no source won't have a natural aspect ratio,
but aspect-ratio: auto should still fall back to a ratio of 300/150.
used_size_as_if_inline_element_from_content_box_sizes() was already
handling this, but other consumers of preferred_aspect_ratio() were
wrong. In particular, this resulted in a 0px wide inline-block:
<div style="display: inline-block; border: solid">
<video style="height: 100px; background: cyan"></video>
</div>So this patch moves the fallback into preferred_aspect_ratio().
Signed-off-by: Oriol Brufau obrufau@igalia.com