LibWeb: Resolve vertical margins against containing block width

We were incorrectly resolving them against the available width, which
may or may not be the same as the containing block width.

The specification for these properties says that percentages resolve
against the containing block width, so that's what we should do.

Userland/Libraries/LibWeb/Layout/BlockFormattingContext.cpp

@@ -300,7 +300,7 @@ void BlockFormattingContext::compute_width_for_block_level_replaced_element_in_n
 
 void BlockFormattingContext::compute_height(Box const& box, AvailableSpace const& available_space)
 {
-    resolve_vertical_box_model_metrics(box, available_space, m_state);
+    resolve_vertical_box_model_metrics(box, m_state);
 
     auto const& computed_values = box.computed_values();
     auto containing_block_height = CSS::Length::make_px(available_space.height.to_px());
@@ -370,7 +370,7 @@ void BlockFormattingContext::layout_block_level_box(Box const& box, BlockContain
     compute_width(box, available_space, layout_mode);
 
     if (is<ReplacedBox>(box) || is<BlockContainer>(box))
-        place_block_level_element_in_normal_flow_vertically(box, available_space);
+        place_block_level_element_in_normal_flow_vertically(box);
 
     if (box_state.has_definite_height()) {
         compute_height(box, available_space);
@@ -426,11 +426,11 @@ void BlockFormattingContext::layout_block_level_children(BlockContainer const& b
     }
 }
 
-void BlockFormattingContext::resolve_vertical_box_model_metrics(Box const& box, AvailableSpace const& available_space, LayoutState& state)
+void BlockFormattingContext::resolve_vertical_box_model_metrics(Box const& box, LayoutState& state)
 {
     auto& box_state = state.get_mutable(box);
     auto const& computed_values = box.computed_values();
-    auto width_of_containing_block = CSS::Length::make_px(available_space.width.to_px_or_zero());
+    auto width_of_containing_block = CSS::Length::make_px(containing_block_width_for(box, state));
 
     box_state.margin_top = computed_values.margin().top().resolved(box, width_of_containing_block).to_px(box);
     box_state.margin_bottom = computed_values.margin().bottom().resolved(box, width_of_containing_block).to_px(box);
@@ -440,12 +440,12 @@ void BlockFormattingContext::resolve_vertical_box_model_metrics(Box const& box,
     box_state.padding_bottom = computed_values.padding().bottom().resolved(box, width_of_containing_block).to_px(box);
 }
 
-void BlockFormattingContext::place_block_level_element_in_normal_flow_vertically(Box const& child_box, AvailableSpace const& available_space)
+void BlockFormattingContext::place_block_level_element_in_normal_flow_vertically(Box const& child_box)
 {
     auto& box_state = m_state.get_mutable(child_box);
     auto const& computed_values = child_box.computed_values();
 
-    resolve_vertical_box_model_metrics(child_box, available_space, m_state);
+    resolve_vertical_box_model_metrics(child_box, m_state);
 
     auto y = FormattingContext::compute_box_y_position_with_respect_to_siblings(child_box);
 
@@ -566,7 +566,7 @@ void BlockFormattingContext::layout_floating_box(Box const& box, BlockContainer
         auto y = line_builder->y_for_float_to_be_inserted_here(box);
         box_state.set_content_y(y + box_state.margin_box_top());
     } else {
-        place_block_level_element_in_normal_flow_vertically(box, available_space);
+        place_block_level_element_in_normal_flow_vertically(box);
         place_block_level_element_in_normal_flow_horizontally(box, available_space);
     }
 

Userland/Libraries/LibWeb/Layout/BlockFormattingContext.h

@@ -67,9 +67,9 @@ private:
     void layout_block_level_children(BlockContainer const&, LayoutMode, AvailableSpace const&);
     void layout_inline_children(BlockContainer const&, LayoutMode, AvailableSpace const&);
 
-    static void resolve_vertical_box_model_metrics(Box const& box, AvailableSpace const&, LayoutState&);
+    static void resolve_vertical_box_model_metrics(Box const& box, LayoutState&);
     void place_block_level_element_in_normal_flow_horizontally(Box const& child_box, AvailableSpace const&);
-    void place_block_level_element_in_normal_flow_vertically(Box const& child_box, AvailableSpace const&);
+    void place_block_level_element_in_normal_flow_vertically(Box const&);
 
     void layout_list_item_marker(ListItemBox const&);