LibWeb: Let Paintable perform the painting

This patch adds a bunch of Paintable subclasses, each corresponding to
the Layout::Node subclasses that had a paint() override. All painting
logic is moved from layout nodes into their corresponding paintables.

Paintables are now created by asking a Layout::Box to produce one:

    static NonnullOwnPtr<Paintable> Layout::Box::create_paintable()

Note that inline nodes still have their painting logic. Since they
are not boxes, and all paintables have a corresponding box, we'll need
to come up with some other solution for them.

1 files changed, 2 insertions, 1 deletions

diff --git a/Userland/Libraries/LibWeb/Layout/CanvasBox.h b/Userland/Libraries/LibWeb/Layout/CanvasBox.h
index 3e1d9a5ab5..8f0df09308 100644
--- a/Userland/Libraries/LibWeb/Layout/CanvasBox.h
+++ b/Userland/Libraries/LibWeb/Layout/CanvasBox.h
@@ -17,9 +17,10 @@ public:
     virtual ~CanvasBox() override;
 
     virtual void prepare_for_replaced_layout() override;
-    virtual void paint(PaintContext&, Painting::PaintPhase) override;
 
     const HTML::HTMLCanvasElement& dom_node() const { return static_cast<const HTML::HTMLCanvasElement&>(ReplacedBox::dom_node()); }
+
+    virtual OwnPtr<Painting::Paintable> create_paintable() const override;
 };
 
 }