Make Galleys share Rows and store their offsets

crates/epaint/src/shape_transform.rs

@@ -88,7 +88,8 @@ pub fn adjust_colors(
 
             if !galley.is_empty() {
                 let galley = std::sync::Arc::make_mut(galley);
-                for row in &mut galley.rows {
+                for (row, _) in &mut galley.rows {
+                    let row = Arc::make_mut(row);
                     for vertex in &mut row.visuals.mesh.vertices {
                         adjust_color(&mut vertex.color);
                     }