HTMLStyleElement will not parse a style element created in Javascript until it
is attached to the DOM.
I added a reftest for the given cases:
* a style element is defined in the HTML code,
* a style element is created in Javascript, CSS content is added to the
element and the element is later attached to the document,
* a style element is created in Javascript, attached to the document and
later CSS content is added to the element,
* a style element is created in Javascript, CSS content is added to the
* element but the element is never attached to the document.
