LibWeb: Make style containment influence quotes

Author: https://github.com/Psychpsyo
Commit: 402d8220dd
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/3480
Reviewed-by: https://github.com/AtkinsSJ ✅

Libraries/LibWeb/Layout/TreeBuilder.cpp

@@ -573,6 +573,8 @@ void TreeBuilder::update_layout_tree(DOM::Node& dom_node, TreeBuilder::Context&
         return false;
     }();
 
+    auto prior_quote_nesting_level = m_quote_nesting_level;
+
     if (should_create_layout_node)
         update_layout_tree_before_children(dom_node, *layout_node, context, element_has_content_visibility_hidden);
 
@@ -617,6 +619,14 @@ void TreeBuilder::update_layout_tree(DOM::Node& dom_node, TreeBuilder::Context&
             restructure_block_node_in_inline_parent(static_cast<NodeWithStyleAndBoxModelMetrics&>(*layout_node));
     }
 
+    // https://www.w3.org/TR/css-contain-2/#containment-style
+    // Giving an element style containment has the following effects:
+    // 2. The effects of the 'content' property’s 'open-quote', 'close-quote', 'no-open-quote' and 'no-close-quote' must
+    //    be scoped to the element’s sub-tree.
+    if (dom_node.is_element() && (static_cast<DOM::Element&>(dom_node)).has_style_containment()) {
+        m_quote_nesting_level = prior_quote_nesting_level;
+    }
+
     dom_node.set_needs_layout_tree_update(false);
     dom_node.set_child_needs_layout_tree_update(false);
 }