LibWeb: Schedule repainting from EventLoop::process()

In this change, updating layout and painting are moved to the EventLoop
processing steps. This modification allows the addition of resize
observation dispatching that needs to happen in event loop processing
steps and must occur in the following order relative to layout and
painting:

1. Update layout.
2. Gather and broadcast resize observations.
3. Paint.

Userland/Libraries/LibWeb/SVG/SVGDecodedImageData.cpp

@@ -48,6 +48,7 @@ public:
     virtual CSS::PreferredColorScheme preferred_color_scheme() const override { return m_host_page.client().preferred_color_scheme(); }
     virtual void request_file(FileRequest) override { }
     virtual void paint(DevicePixelRect const&, Gfx::Bitmap&, Web::PaintOptions = {}) override { }
+    virtual void schedule_repaint() override { }
 
 private:
     explicit SVGPageClient(Page& host_page)