LibJS+LibWeb: Move native properties to separate getters/setters

This was a bit cumbersome now, but it gets us closer to a format suited
for code generation.

Libraries/LibWeb/Bindings/CanvasRenderingContext2DWrapper.h

@@ -43,6 +43,8 @@ private:
     virtual const char* class_name() const override { return "CanvasRenderingContext2DWrapper"; }
 
     static JS::Value fill_rect(JS::Interpreter&);
+    static JS::Value fill_style_getter(JS::Interpreter&);
+    static void fill_style_setter(JS::Interpreter&, JS::Value);
 
     NonnullRefPtr<CanvasRenderingContext2D> m_impl;
 };