layout: Only create a LayoutContext if restyling (#37726)

The creation of `LayoutContext` does more work than necessary if layout
just needs to do something like make a display list and not restyle and
relayout. This change makes it so that these kind of non-restyle layouts
do not need to create a display list. In addition, the creation of
`LayoutContext` is better encapsulate

Testing: This should not change observable behavior and is thus covered
by existing WPT tests.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>

components/layout/fragment_tree/fragment_tree.rs

@@ -59,6 +59,7 @@ impl FragmentTree {
         let mut animations = layout_context.style_context.animations.sets.write();
         let mut invalid_animating_nodes: FxHashSet<_> = animations.keys().cloned().collect();
         let mut image_animations = layout_context
+            .image_resolver
             .node_to_animating_image_map
             .write()
             .to_owned();