First of all, the effective command value was wrong, since there is no
relevant CSS property for the underline command. Instead, we should
directly use the text-decoration property. This then allows us to
implement reordering of modifiable elements.
We also need to "change the element to a span", which is quite annoying
to do. Instead, it mimics what would have happened by moving children
and copying attributes.
There are some regressions, but overall this is another big step towards
the right track. The regressions look related to tricky edge cases that
I am not even sure other browsers handle.
Part of #25005
Testing: WPT
Signed-off-by: Tim van der Lippe <tvanderlippe@gmail.com>
d096560b51