Implement internal pseudo element, which would be resolved as a
"Implemented Pseudo Element" within style computation. This is an
concrete element that would has a primary style after the style
computation, but could match and style resolved like an pseudo element.
Therefore, it would have a different behavior compared to how does
`pseudo`s that `ServoLayoutNode` had. Where they would not have a
concrete element behind it. Note that, due to the nature of these pseudo
elements residing inside a UA widget, these pseudo elements would
therefore not be accessible in JavaScript by default.
This kind of element is required in order to implement the [form control
pseudo element](https://drafts.csswg.org/css-forms-1/#pseudo-elements)
like `::placeholder`, `::color-swatch`, `::field-text`, etc.
See [this docs](https://hackmd.io/@ChaKweTiau/BJ3zRdLQlg) for more
details of the implementation.
Then, the implemented pseudo element is utilized to implement style
matching for input `type=text`.
Servo's side of: https://github.com/servo/stylo/pull/212
Testing: No WPT regression.
---------
Signed-off-by: stevennovaryo <steven.novaryo@gmail.com>
In quirks mode, the ::marker of a bare `<li>` should be
`list-style-position: inside`,
Testing: Some WPT improvement
Signed-off-by: Oriol Brufau <obrufau@igalia.com>
This change adds a shadow-tree widget for `<input type=color>` elements.
It also involves some changes to the way layout interacts with the DOM,
because currently all `input` and `textarea` elements are rendered as
plain text and their descendants are ignored. This obviously doesn't
work for `<input type={color, date, range, etc}>`.

<details><summary>HTML used for the screenshot above</summary>
```html
<input type=color>
```
</details>
Testing: I doubt that this affects WPT tests, because the appearance and
behaviour of the widget is almost entirely unspecified.
---------
Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>