LibWeb: Accept paintable instead of layout node in paint_background()

After InlinePaintable is gone it's possible to make this function accept
a PaintableBox instead of more broad
Layout::NodeWithStyleAndBoxModelMetrics type.

Userland/Libraries/LibWeb/Painting/BackgroundPainting.cpp

@@ -48,17 +48,17 @@ static RefPtr<DisplayList> compute_text_clip_paths(PaintContext& context, Painta
     return text_clip_paths;
 }
 
-static BackgroundBox get_box(CSS::BackgroundBox box_clip, BackgroundBox border_box, auto const& layout_node)
+static BackgroundBox get_box(CSS::BackgroundBox box_clip, BackgroundBox border_box, auto const& paintable_box)
 {
     auto box = border_box;
     switch (box_clip) {
     case CSS::BackgroundBox::ContentBox: {
-        auto& padding = layout_node.box_model().padding;
+        auto& padding = paintable_box.box_model().padding;
         box.shrink(padding.top, padding.right, padding.bottom, padding.left);
         [[fallthrough]];
     }
     case CSS::BackgroundBox::PaddingBox: {
-        auto& border = layout_node.box_model().border;
+        auto& border = paintable_box.box_model().border;
         box.shrink(border.top, border.right, border.bottom, border.left);
         [[fallthrough]];
     }
@@ -69,13 +69,13 @@ static BackgroundBox get_box(CSS::BackgroundBox box_clip, BackgroundBox border_b
 }
 
 // https://www.w3.org/TR/css-backgrounds-3/#backgrounds
-void paint_background(PaintContext& context, Layout::NodeWithStyleAndBoxModelMetrics const& layout_node, CSS::ImageRendering image_rendering, ResolvedBackground resolved_background, BorderRadiiData const& border_radii)
+void paint_background(PaintContext& context, PaintableBox const& paintable_box, CSS::ImageRendering image_rendering, ResolvedBackground resolved_background, BorderRadiiData const& border_radii)
 {
     auto& display_list_recorder = context.display_list_recorder();
 
     DisplayListRecorderStateSaver state { display_list_recorder };
     if (resolved_background.needs_text_clip) {
-        auto display_list = compute_text_clip_paths(context, *layout_node.first_paintable(), resolved_background.background_rect.location());
+        auto display_list = compute_text_clip_paths(context, paintable_box, resolved_background.background_rect.location());
         auto rect = context.rounded_device_rect(resolved_background.background_rect);
         display_list_recorder.add_mask(move(display_list), rect.to_type<int>());
     }
@@ -102,10 +102,10 @@ void paint_background(PaintContext& context, Layout::NodeWithStyleAndBoxModelMet
         DevicePixels right { 0 };
     } clip_shrink;
 
-    auto border_top = layout_node.computed_values().border_top();
-    auto border_bottom = layout_node.computed_values().border_bottom();
-    auto border_left = layout_node.computed_values().border_left();
-    auto border_right = layout_node.computed_values().border_right();
+    auto border_top = paintable_box.computed_values().border_top();
+    auto border_bottom = paintable_box.computed_values().border_bottom();
+    auto border_left = paintable_box.computed_values().border_left();
+    auto border_right = paintable_box.computed_values().border_right();
 
     if (border_top.color.alpha() == 255 && border_bottom.color.alpha() == 255
         && border_left.color.alpha() == 255 && border_right.color.alpha() == 255) {
@@ -120,7 +120,7 @@ void paint_background(PaintContext& context, Layout::NodeWithStyleAndBoxModelMet
         DisplayListRecorderStateSaver state { display_list_recorder };
 
         // Clip
-        auto clip_box = get_box(layer.clip, border_box, layout_node);
+        auto clip_box = get_box(layer.clip, border_box, paintable_box);
 
         CSSPixelRect const& css_clip_rect = clip_box.rect;
         auto clip_rect = context.rounded_device_rect(css_clip_rect);
@@ -139,15 +139,12 @@ void paint_background(PaintContext& context, Layout::NodeWithStyleAndBoxModelMet
 
         switch (layer.attachment) {
         case CSS::BackgroundAttachment::Fixed:
-            background_positioning_area.set_location(layout_node.root().navigable()->viewport_scroll_offset());
+            background_positioning_area.set_location(paintable_box.layout_node().root().navigable()->viewport_scroll_offset());
             break;
         case CSS::BackgroundAttachment::Local:
-            if (is<Layout::Box>(layout_node)) {
-                auto const* paintable_box = static_cast<Layout::Box const&>(layout_node).paintable_box();
-                if (paintable_box && !paintable_box->is_viewport()) {
-                    auto scroll_offset = paintable_box->scroll_offset();
-                    background_positioning_area.translate_by(-scroll_offset.x(), -scroll_offset.y());
-                }
+            if (!paintable_box.is_viewport()) {
+                auto scroll_offset = paintable_box.scroll_offset();
+                background_positioning_area.translate_by(-scroll_offset.x(), -scroll_offset.y());
             }
             break;
         case CSS::BackgroundAttachment::Scroll:
@@ -244,7 +241,7 @@ void paint_background(PaintContext& context, Layout::NodeWithStyleAndBoxModelMet
         CSSPixels initial_image_x = image_rect.x();
         CSSPixels image_y = image_rect.y();
 
-        image.resolve_for_size(layout_node, image_rect.size());
+        image.resolve_for_size(paintable_box.layout_node_with_style_and_box_metrics(), image_rect.size());
 
         auto for_each_image_device_rect = [&](auto callback) {
             while (image_y < css_clip_rect.bottom()) {

Userland/Libraries/LibWeb/Painting/BackgroundPainting.h

@@ -47,6 +47,6 @@ struct ResolvedBackground {
 
 ResolvedBackground resolve_background_layers(Vector<CSS::BackgroundLayerData> const& layers, Layout::NodeWithStyleAndBoxModelMetrics const& layout_node, Color background_color, CSSPixelRect const& border_rect, BorderRadiiData const& border_radii);
 
-void paint_background(PaintContext&, Layout::NodeWithStyleAndBoxModelMetrics const&, CSS::ImageRendering, ResolvedBackground resolved_background, BorderRadiiData const&);
+void paint_background(PaintContext&, PaintableBox const&, CSS::ImageRendering, ResolvedBackground resolved_background, BorderRadiiData const&);
 
 }

Userland/Libraries/LibWeb/Painting/PaintableBox.cpp

@@ -476,7 +476,7 @@ void PaintableBox::paint_background(PaintContext& context) const
     if (layout_node_with_style_and_box_metrics().is_body() && document().html_element()->should_use_body_background_properties())
         return;
 
-    Painting::paint_background(context, layout_node_with_style_and_box_metrics(), computed_values().image_rendering(), m_resolved_background, normalized_border_radii_data());
+    Painting::paint_background(context, *this, computed_values().image_rendering(), m_resolved_background, normalized_border_radii_data());
 }
 
 void PaintableBox::paint_box_shadow(PaintContext& context) const