Make some foo.h headers usable without foo-inl.h header.

src/heap/objects-visiting.h

Index: src/heap/objects-visiting.h
diff --git a/src/heap/objects-visiting.h b/src/heap/objects-visiting.h
index 57715efe1e2e8b730cd626aa8330c1953508a87c..953d89681bb3ddbd62b5a6aec68d92c5d6bdda96 100644
--- a/src/heap/objects-visiting.h
+++ b/src/heap/objects-visiting.h
@@ -110,11 +110,7 @@ class StaticVisitorBase : public AllStatic {
                                 bool has_unboxed_fields);
 
   // Determine which specialized visitor should be used for given map.
-  static VisitorId GetVisitorId(Map* map) {
-    return GetVisitorId(
-        map->instance_type(), map->instance_size(),
-        FLAG_unbox_double_fields && !map->HasFastPointerLayout());
-  }
+  static VisitorId GetVisitorId(Map* map);
 
   // For visitors that allow specialization by size calculate VisitorId based
   // on size, base visitor id and generic visitor id.