[json] handle proxies in BasicJsonSerializer.

src/builtins.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/builtins.h"
 
 #include "src/api-arguments.h"
 #include "src/api-natives.h"
 #include "src/api.h"
 #include "src/base/once.h"
@@ skipping 1070 matching lines @@
  */
 bool IterateElements(Isolate* isolate, Handle<JSReceiver> receiver,
                      ArrayConcatVisitor* visitor) {
   uint32_t length = 0;
 
   if (receiver->IsJSArray()) {
     Handle<JSArray> array = Handle<JSArray>::cast(receiver);
     length = static_cast<uint32_t>(array->length()->Number());
   } else {
     Handle<Object> val;
-    Handle<Object> key = isolate->factory()->length_string();
     ASSIGN_RETURN_ON_EXCEPTION_VALUE(
-        isolate, val, Runtime::GetObjectProperty(isolate, receiver, key),
-        false);
-    ASSIGN_RETURN_ON_EXCEPTION_VALUE(isolate, val,
-                                     Object::ToLength(isolate, val), false);
+        isolate, val, Object::GetLengthFromArrayLike(isolate, receiver), false);
     // TODO(caitp): Support larger element indexes (up to 2^53-1).
     if (!val->ToUint32(&length)) {
       length = 0;
     }
     // TODO(cbruni): handle other element kind as well
     return IterateElementsSlow(isolate, receiver, length, visitor);
   }
 
   if (!HasOnlySimpleElements(isolate, *receiver)) {
     return IterateElementsSlow(isolate, receiver, length, visitor);
@@ skipping 4413 matching lines @@
 BUILTIN_LIST_T(DEFINE_BUILTIN_ACCESSOR_T)
 BUILTIN_LIST_H(DEFINE_BUILTIN_ACCESSOR_H)
 BUILTIN_LIST_DEBUG_A(DEFINE_BUILTIN_ACCESSOR_A)
 #undef DEFINE_BUILTIN_ACCESSOR_C
 #undef DEFINE_BUILTIN_ACCESSOR_A
 #undef DEFINE_BUILTIN_ACCESSOR_T
 #undef DEFINE_BUILTIN_ACCESSOR_H
 
 }  // namespace internal
 }  // namespace v8