[keys] Simplify KeyAccumulator

src/json-stringifier.cc

 // Copyright 2016 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/json-stringifier.h"
 
 #include "src/conversions.h"
 #include "src/lookup.h"
 #include "src/messages.h"
 #include "src/objects-inl.h"
@@ skipping 526 matching lines @@
   StackPop();
   return SUCCESS;
 }
 
 BasicJsonStringifier::Result BasicJsonStringifier::SerializeJSReceiverSlow(
     Handle<JSReceiver> object) {
   Handle<FixedArray> contents = property_list_;
   if (contents.is_null()) {
     ASSIGN_RETURN_ON_EXCEPTION_VALUE(
         isolate_, contents,
-        JSReceiver::GetKeys(object, OWN_ONLY, ENUMERABLE_STRINGS), EXCEPTION);
+        KeyAccumulator::GetKeys(object, OWN_ONLY, ENUMERABLE_STRINGS),
+        EXCEPTION);
   }
-
   builder_.AppendCharacter('{');
   Indent();
   bool comma = false;
   for (int i = 0; i < contents->length(); i++) {
     Object* key = contents->get(i);
     Handle<String> key_handle;
     MaybeHandle<Object> maybe_property;
     if (key->IsString()) {
       key_handle = Handle<String>(String::cast(key), isolate_);
       maybe_property = Object::GetPropertyOrElement(object, key_handle);
@@ skipping 144 matching lines @@
     if (object->IsOneByteRepresentationUnderneath()) {
       SerializeString_<uint8_t, uc16>(object);
     } else {
       SerializeString_<uc16, uc16>(object);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8