8235842: Shenandoah: Implement native LRB for narrow oop

Reviewed-by: rkennke
diff --git a/src/hotspot/share/gc/shenandoah/shenandoahBarrierSet.cpp b/src/hotspot/share/gc/shenandoah/shenandoahBarrierSet.cpp
index 4d0bfa4..153af9c 100644
--- a/src/hotspot/share/gc/shenandoah/shenandoahBarrierSet.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahBarrierSet.cpp
@@ -252,9 +252,7 @@
 }
 
 oop ShenandoahBarrierSet::load_reference_barrier_native(oop obj, narrowOop* load_addr) {
-  // Assumption: narrow oop version should not be used anywhere.
-  ShouldNotReachHere();
-  return NULL;
+  return load_reference_barrier_native_impl(obj, load_addr);
 }
 
 template <class T>