WebContent+LibWeb: Add an option to disable painting viewport scrollbars

Author: https://github.com/tcl3
Commit: 639ed5a052
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2962
Reviewed-by: https://github.com/AtkinsSJ ✅

Libraries/LibWeb/Painting/PaintableBox.h

@@ -21,6 +21,8 @@
 
 namespace Web::Painting {
 
+extern bool g_paint_viewport_scrollbars;
+
 class PaintableBox : public Paintable
     , public ClippableAndScrollable {
     GC_CELL(PaintableBox, Paintable);