LibWeb: Add pointer from BFC::FloatingBox to its UsedValues

This will allow us to skip a lot more hash lookups.

Userland/Libraries/LibWeb/Layout/BlockFormattingContext.cpp

@@ -1058,6 +1058,7 @@ void BlockFormattingContext::layout_floating_box(Box const& box, BlockContainer
         auto top_margin_edge = y - box_state.margin_box_top();
         side_data.all_boxes.append(adopt_own(*new FloatingBox {
             .box = box,
+            .used_values = box_state,
             .offset_from_edge = offset_from_edge,
             .top_margin_edge = top_margin_edge,
             .bottom_margin_edge = y + box_state.content_height() + box_state.margin_box_bottom(),

Userland/Libraries/LibWeb/Layout/BlockFormattingContext.h

@@ -89,6 +89,9 @@ private:
 
     struct FloatingBox {
         JS::NonnullGCPtr<Box const> box;
+
+        LayoutState::UsedValues& used_values;
+
         // Offset from left/right edge to the left content edge of `box`.
         CSSPixels offset_from_edge { 0 };