LibWeb: Resolve CSS inset properties when entering inline-flow elements

We don't actually apply the insets anywhere yet, but at least now they
are available in the node's layout state.

Userland/Libraries/LibWeb/Layout/FormattingContext.h

@@ -96,6 +96,8 @@ public:
     virtual CSSPixelPoint calculate_static_position(Box const&) const;
     bool can_skip_is_anonymous_text_run(Box&);
 
+    void compute_inset(NodeWithStyleAndBoxModelMetrics const&);
+
 protected:
     FormattingContext(Type, LayoutState&, Box const&, FormattingContext* parent = nullptr);
 
@@ -106,7 +108,6 @@ protected:
     [[nodiscard]] bool should_treat_max_height_as_none(Box const&, AvailableSize const&) const;
 
     OwnPtr<FormattingContext> layout_inside(Box const&, LayoutMode, AvailableSpace const&);
-    void compute_inset(Box const& box);
 
     struct SpaceUsedByFloats {
         CSSPixels left { 0 };

Userland/Libraries/LibWeb/Layout/InlineLevelIterator.cpp

@@ -42,6 +42,9 @@ void InlineLevelIterator::enter_node_with_box_model_metrics(Layout::NodeWithStyl
     m_extra_leading_metrics->border += used_values.border_left;
     m_extra_leading_metrics->padding += used_values.padding_left;
 
+    // Now's our chance to resolve the inset properties for this node.
+    m_inline_formatting_context.compute_inset(node);
+
     m_box_model_node_stack.append(node);
 }