Take Event by reference in Widget::update

widget/src/button.rs

@@ -275,7 +275,7 @@ where
     fn update(
         &mut self,
         tree: &mut Tree,
-        event: Event,
+        event: &Event,
         layout: Layout<'_>,
         cursor: mouse::Cursor,
         renderer: &Renderer,
@@ -285,7 +285,7 @@ where
     ) {
         self.content.as_widget_mut().update(
             &mut tree.children[0],
-            event.clone(),
+            event,
             layout.children().next().unwrap(),
             cursor,
             renderer,