Revert "Remove layout method from core::Renderer trait"

This reverts commit 2128472c2a.

core/src/renderer.rs

@@ -5,13 +5,26 @@ mod null;
 #[cfg(debug_assertions)]
 pub use null::Null;
 
-use crate::{Background, BorderRadius, Color, Rectangle, Vector};
+use crate::layout;
+use crate::{Background, BorderRadius, Color, Element, Rectangle, Vector};
 
 /// A component that can be used by widgets to draw themselves on a screen.
 pub trait Renderer: Sized {
     /// The supported theme of the [`Renderer`].
     type Theme;
 
+    /// Lays out the elements of a user interface.
+    ///
+    /// You should override this if you need to perform any operations before or
+    /// after layouting. For instance, trimming the measurements cache.
+    fn layout<Message>(
+        &mut self,
+        element: &Element<'_, Message, Self>,
+        limits: &layout::Limits,
+    ) -> layout::Node {
+        element.as_widget().layout(self, limits)
+    }
+
     /// Draws the primitives recorded in the given closure in a new layer.
     ///
     /// The layer will clip its contents to the provided `bounds`.