[runtime] Make elements backing store for arguments non-holey.

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 1336 matching lines @@
   {  // --- sloppy arguments map
     // Make sure we can recognize argument objects at runtime.
     // This is done by introducing an anonymous function with
     // class_name equals 'Arguments'.
     Handle<String> arguments_string = factory->Arguments_string();
     Handle<Code> code(isolate->builtins()->builtin(Builtins::kIllegal));
     Handle<JSFunction> function = factory->NewFunctionWithoutPrototype(
         arguments_string, code);
     function->shared()->set_instance_class_name(*arguments_string);
 
-    Handle<Map> map =
-        factory->NewMap(JS_OBJECT_TYPE, Heap::kSloppyArgumentsObjectSize);
+    Handle<Map> map = factory->NewMap(
+        JS_OBJECT_TYPE, Heap::kSloppyArgumentsObjectSize, FAST_ELEMENTS);
     // Create the descriptor array for the arguments object.
     Map::EnsureDescriptorSlack(map, 2);
 
     {  // length
       DataDescriptor d(factory->length_string(), Heap::kArgumentsLengthIndex,
                        DONT_ENUM, Representation::Tagged());
       map->AppendDescriptor(&d);
     }
     {  // callee
       DataDescriptor d(factory->callee_string(), Heap::kArgumentsCalleeIndex,
@@ skipping 38 matching lines @@
 
     Handle<JSFunction> poison = GetStrictArgumentsPoisonFunction();
 
     // Install the ThrowTypeError functions.
     callee->set_getter(*poison);
     callee->set_setter(*poison);
     caller->set_getter(*poison);
     caller->set_setter(*poison);
 
     // Create the map. Allocate one in-object field for length.
-    Handle<Map> map = factory->NewMap(JS_OBJECT_TYPE,
-                                      Heap::kStrictArgumentsObjectSize);
+    Handle<Map> map = factory->NewMap(
+        JS_OBJECT_TYPE, Heap::kStrictArgumentsObjectSize, FAST_ELEMENTS);
     // Create the descriptor array for the arguments object.
     Map::EnsureDescriptorSlack(map, 3);
 
     {  // length
       DataDescriptor d(factory->length_string(), Heap::kArgumentsLengthIndex,
                        DONT_ENUM, Representation::Tagged());
       map->AppendDescriptor(&d);
     }
     {  // callee
       AccessorConstantDescriptor d(factory->callee_string(), callee,
@@ skipping 1805 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8