StructTraits optimizations

cc/ipc/selection_struct_traits.h

Index: cc/ipc/selection_struct_traits.h
diff --git a/cc/ipc/selection_struct_traits.h b/cc/ipc/selection_struct_traits.h
index d4b29ea363723c11460ea0a724076629224f0683..c5d52f780fc48537b9e17958380b8d2ab169bc6a 100644
--- a/cc/ipc/selection_struct_traits.h
+++ b/cc/ipc/selection_struct_traits.h
@@ -12,12 +12,12 @@ namespace mojo {
 
 template <>
 struct StructTraits<cc::mojom::Selection, cc::Selection<gfx::SelectionBound>> {
-  static gfx::SelectionBound start(
+  static const gfx::SelectionBound& start(
       const cc::Selection<gfx::SelectionBound>& selection) {
     return selection.start;
   }
 
-  static gfx::SelectionBound end(
+  static const gfx::SelectionBound& end(
       const cc::Selection<gfx::SelectionBound>& selection) {
     return selection.end;
   }