The spec recently changed to match browsers better. There's currently
not much interop in exact details of how this work. This brings us in
line with the spec except for the limit of 1000 on the span attribute.
The added textarea failures are spurious, because I'm not updating our
local tests in this commit. The new tests are submitted upstream at
<https://github.com/w3c/web-platform-tests/pull/3518>.
MozReview-Commit-ID: 1L8aUtF47Qi
This changes to match the spec, which also aligns the behavior of get
and set (get already maps out-of-range values to the default value).
There is currently no interoperable behavior here, but this aligns us
with IE -- tested in 11, hopefully true for Edge too.
On the way, I also fixed the fact that video's height and width were
being treated as signed.
