diff --git a/renderer/src/scene.rs b/renderer/src/scene.rs
index 98402e56..33f6418e 100644
--- a/renderer/src/scene.rs
+++ b/renderer/src/scene.rs
@@ -133,6 +133,8 @@ impl Scene {
             outline.dilate(options.dilation);
         }
 
+        // TODO(pcwalton): Fold this into previous passes to avoid unnecessary clones during
+        // monotonic conversion.
         outline.prepare_for_tiling(self.view_box);
         outline
     }