Introduce {FAST,SLOW}_STRING_WRAPPER_ELEMENTS

src/bootstrapper.cc

 // Copyright 2014 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/bootstrapper.h"
 
 #include "src/accessors.h"
 #include "src/api-natives.h"
 #include "src/code-stubs.h"
 #include "src/extensions/externalize-string-extension.h"
@@ skipping 1223 matching lines @@
         isolate->initial_object_prototype(), Builtins::kStringConstructor);
     string_fun->shared()->set_construct_stub(
         *isolate->builtins()->StringConstructor_ConstructStub());
     string_fun->shared()->DontAdaptArguments();
     string_fun->shared()->set_length(1);
     InstallWithIntrinsicDefaultProto(isolate, string_fun,
                                      Context::STRING_FUNCTION_INDEX);
 
     Handle<Map> string_map =
         Handle<Map>(native_context()->string_function()->initial_map());
+    string_map->set_elements_kind(FAST_STRING_WRAPPER_ELEMENTS);
     Map::EnsureDescriptorSlack(string_map, 1);
 
     PropertyAttributes attribs = static_cast<PropertyAttributes>(
         DONT_ENUM | DONT_DELETE | READ_ONLY);
     Handle<AccessorInfo> string_length(
         Accessors::StringLengthInfo(isolate, attribs));
 
     {  // Add length.
       AccessorConstantDescriptor d(factory->length_string(), string_length,
                                    attribs);
@@ skipping 2376 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8