Introduce a visible_bounds parameter to Element::paint

We're not using this yet but this will be useful to avoid rendering
unnecessary portions of text.

gpui/src/elements/event_handler.rs

@@ -44,10 +44,11 @@ impl Element for EventHandler {
     fn paint(
         &mut self,
         bounds: RectF,
+        visible_bounds: RectF,
         _: &mut Self::LayoutState,
         cx: &mut PaintContext,
     ) -> Self::PaintState {
-        self.child.paint(bounds.origin(), cx);
+        self.child.paint(bounds.origin(), visible_bounds, cx);
     }
 
     fn dispatch_event(