Fix changed expectation in Heap::AllowToBeMigrated.

src/heap-inl.h

Index: src/heap-inl.h
diff --git a/src/heap-inl.h b/src/heap-inl.h
index 77538cac52cd60ac3d3b135b8233d54511976524..fdf86ff2cc85c18809afb6d91f0112d6835ce02f 100644
--- a/src/heap-inl.h
+++ b/src/heap-inl.h
@@ -469,9 +469,8 @@ bool Heap::AllowedToBeMigrated(HeapObject* obj, AllocationSpace dst) {
     case NEW_SPACE:
       return dst == src || dst == TargetSpaceId(type);
     case OLD_POINTER_SPACE:
-      return dst == src &&
-          (dst == TargetSpaceId(type) || obj->IsFiller() ||
-          (obj->IsExternalString() && ExternalString::cast(obj)->is_short()));
+      return dst == src && (dst == TargetSpaceId(type) || obj->IsFiller() ||
+                            (obj->IsExternalString()));
     case OLD_DATA_SPACE:
       return dst == src && dst == TargetSpaceId(type);
     case CODE_SPACE: