LibWeb: Resolve CSS transform properties during layout commit

Now, instead of resolving "transform" and "transform-origin" during the
construction of the stacking context tree, we do so during the layout
commit.

This is part of a refactoring effort to make the paintable tree
independent from the layout tree.

Userland/Libraries/LibWeb/Layout/LayoutState.h

@@ -189,6 +189,7 @@ private:
     void resolve_border_radii();
     void resolve_box_shadow_data();
     void resolve_text_shadows(Vector<Painting::PaintableWithLines&> const& paintables_with_lines);
+    void resolve_css_transform();
 };
 
 }