This is a part of refactoring towards making the paintable tree
independent of the layout tree. Now, instead of transferring text
fragments from the layout tree to the paintable tree during the layout
commit phase, we allocate separate PaintableFragments that contain only
the information necessary for painting. Doing this also allows us to
get rid LineBoxes, as they are used only during layout.
This makes use of the new Gfx::Path::text() to handle SVG text elements,
with this text is just a regular path, and can be manipulated like any
other graphics element.
This removes the SVGTextPaintable and makes both <text> and geometry
elements use a new (shared) SVGPathPaintable. This is identical to the
old SVGGeometryPaintable. This simplifies painting as once something is
resolved to a Gfx::Path, the painting logic is the same.
This patch just adds the new root paintable and updates the tests
expectations. The next patch will move painting logic from the layout
viewport to the paint viewport.
SVG presentation attributes are parsed as CSS values, so we also need to
handle CSS variable expansion when handling them.
This (roughly) matches the behavior of other engines. It's also used on
the web, for example on https://stripe.com/ :^)
