A lot (and I mean, really a lot) depends on these constructors.
Therefore, this is the one spaghetti ball that I could extract and
convert all `can_gc` to `cx`. There are some new introductions of
`temp_cx` in the callbacks of the servo parser, but we already had some
in other callbacks.
Part of #40600
Testing: It compiles
Signed-off-by: Tim van der Lippe <tvanderlippe@gmail.com>
In addition to making it so that textual `<input>` and `<textarea>`
share a common shadow DOM structure, this allows styling the
`<textarea>` placeholder. It is now properly shown in grey.
Testing: This fixes a few WPT tests.
Signed-off-by: Martin Robinson <mrobinson@igalia.com>