[json] handle proxies in BasicJsonSerializer.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 3c23e011fc6285453934decd98e884a1f10db89a..3a33996b1bd373be11df8824d1e180a91d230efb 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -719,14 +719,9 @@ MaybeHandle<FixedArray> Object::CreateListFromArrayLike(
   }
   // 4. Let len be ? ToLength(? Get(obj, "length")).
   Handle<JSReceiver> receiver = Handle<JSReceiver>::cast(object);
-  Handle<Object> raw_length_obj;
-  ASSIGN_RETURN_ON_EXCEPTION(
-      isolate, raw_length_obj,
-      JSReceiver::GetProperty(receiver, isolate->factory()->length_string()),
-      FixedArray);
   Handle<Object> raw_length_number;
   ASSIGN_RETURN_ON_EXCEPTION(isolate, raw_length_number,
-                             Object::ToLength(isolate, raw_length_obj),
+                             Object::GetLengthFromArrayLike(isolate, receiver),
                              FixedArray);
   uint32_t len;
   if (!raw_length_number->ToUint32(&len) ||
@@ -773,6 +768,16 @@ MaybeHandle<FixedArray> Object::CreateListFromArrayLike(
 
 
 // static
+MaybeHandle<Object> Object::GetLengthFromArrayLike(Isolate* isolate,
+                                                   Handle<Object> object) {
+  Handle<Object> val;
+  Handle<Object> key = isolate->factory()->length_string();

[Camillo Bruni, 2016/05/20 09:55:55]

I hope this is obvious enough that this is too slow to be used with JSArrays ;)

[Yang, 2016/05/20 12:47:18]

Unfortunately this is actually being used for JSArrays, when called from
Object::CreateListFromArrayLike. If you want, I can work on a separate CL to add
a fast path for JSArrays here...

+  ASSIGN_RETURN_ON_EXCEPTION(
+      isolate, val, Runtime::GetObjectProperty(isolate, object, key), Object);
+  return Object::ToLength(isolate, val);
+}
+
+// static
 Maybe<bool> JSReceiver::HasProperty(LookupIterator* it) {
   for (; it->IsFound(); it->Next()) {
     switch (it->state()) {