This patch implements `Range::getClientRects` and
`Range::getBoundingClientRect`. Since the rects returned by invoking
getClientRects can be accessed without adding them to the Selection,
`ViewportPaintable::recompute_selection_states` has been updated to
accept a Range as a parameter, rather than acquiring it through the
Document's Selection.
With this change, the following tests now pass:
- wpt[css/cssom-view/range-bounding-client-rect-with-nested-text.html]
- wpt[css/cssom-view/DOMRectList.html]
Note: The test
"css/cssom-view/range-bounding-client-rect-with-display-contents.html"
still fails due to an issue with Element::getClientRects, which will
be addressed in a future commit.
