LibWeb: Paint inspection outline for InlineNodes :^)

This iterates the fragments of the containing block, and paints their
outlines if they are descendants of the InlineNode.

If multiple fragments are adjacent, eg:

```html
<span><b>Well</b> hello <i>friends!</i></span>
```

...then we get a double-thick outline between "Well", " hello " and
"friends!", but we can come back to this after we implement
non-rectangular outlines for the `outline` CSS property.

Userland/Libraries/LibWeb/Layout/InlineNode.cpp

@@ -5,6 +5,7 @@
  */
 
 #include <LibGfx/Painter.h>
+#include <LibWeb/DOM/Document.h>
 #include <LibWeb/DOM/Element.h>
 #include <LibWeb/Layout/BlockBox.h>
 #include <LibWeb/Layout/InlineFormattingContext.h>
@@ -48,4 +49,20 @@ void InlineNode::paint_fragment(PaintContext& context, const LineBoxFragment& fr
     }
 }
 
+void InlineNode::paint(PaintContext& context, PaintPhase phase)
+{
+    auto& painter = context.painter();
+
+    if (phase == PaintPhase::Foreground && document().inspected_node() == dom_node()) {
+        // FIXME: This paints a double-thick border between adjacent fragments, where ideally there
+        //        would be none. Once we implement non-rectangular outlines for the `outline` CSS
+        //        property, we can use that here instead.
+        containing_block()->for_each_fragment([&](auto& fragment) {
+            if (is_inclusive_ancestor_of(fragment.layout_node()))
+                painter.draw_rect(enclosing_int_rect(fragment.absolute_rect()), Color::Magenta);
+            return IterationDecision::Continue;
+        });
+    }
+}
+
 }

Userland/Libraries/LibWeb/Layout/InlineNode.h

@@ -15,6 +15,7 @@ public:
     InlineNode(DOM::Document&, DOM::Element&, NonnullRefPtr<CSS::StyleProperties>);
     virtual ~InlineNode() override;
 
+    virtual void paint(PaintContext&, PaintPhase) override;
     virtual void paint_fragment(PaintContext&, const LineBoxFragment&, PaintPhase) const override;
 
     virtual void split_into_lines(InlineFormattingContext&, LayoutMode) override;