Introduce {FAST,SLOW}_STRING_WRAPPER_ELEMENTS

src/heap/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/heap.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/ast/scopeinfo.h"
 #include "src/base/bits.h"
@@ skipping 3497 matching lines @@
   FixedArray* properties = empty_fixed_array();
 
   // Allocate the JSObject.
   AllocationSpace space = SelectSpace(pretenure);
   JSObject* js_obj = nullptr;
   AllocationResult allocation = Allocate(map, space, allocation_site);
   if (!allocation.To(&js_obj)) return allocation;
 
   // Initialize the JSObject.
   InitializeJSObjectFromMap(js_obj, properties, map);
-  DCHECK(js_obj->HasFastElements() || js_obj->HasFixedTypedArrayElements());
+  DCHECK(js_obj->HasFastElements() || js_obj->HasFixedTypedArrayElements() ||
+         js_obj->HasFastStringWrapperElements());
   return js_obj;
 }
 
 
 AllocationResult Heap::AllocateJSObject(JSFunction* constructor,
                                         PretenureFlag pretenure,
                                         AllocationSite* allocation_site) {
   DCHECK(constructor->has_initial_map());
 
   // Allocate the object based on the constructors initial map.
@@ skipping 2715 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8