[builtins] Also port the Object.prototype.__proto__ accessors to C++.

src/builtins/builtins-object.cc

Index: src/builtins/builtins-object.cc
diff --git a/src/builtins/builtins-object.cc b/src/builtins/builtins-object.cc
index 5899879778ad95eb83d51b3fd13e6c354518b5c0..b0bb1f043d6686ccccff6e397ddbcdd0327b92fd 100644
--- a/src/builtins/builtins-object.cc
+++ b/src/builtins/builtins-object.cc
@@ -722,6 +722,51 @@ BUILTIN(ObjectSetPrototypeOf) {
   return *receiver;
 }
 
+// ES6 section B.2.2.1.1 get Object.prototype.__proto__
+BUILTIN(ObjectPrototypeGetProto) {
+  HandleScope scope(isolate);
+  // 1. Let O be ? ToObject(this value).
+  Handle<JSReceiver> receiver;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, receiver, Object::ToObject(isolate, args.receiver()));
+
+  // 2. Return ? O.[[GetPrototypeOf]]().
+  RETURN_RESULT_OR_FAILURE(isolate,
+                           JSReceiver::GetPrototype(isolate, receiver));
+}
+
+// ES6 section B.2.2.1.2 set Object.prototype.__proto__
+BUILTIN(ObjectPrototypeSetProto) {
+  HandleScope scope(isolate);
+  // 1. Let O be ? RequireObjectCoercible(this value).
+  Handle<Object> object = args.receiver();
+  if (object->IsNull(isolate) || object->IsUndefined(isolate)) {
+    THROW_NEW_ERROR_RETURN_FAILURE(
+        isolate, NewTypeError(MessageTemplate::kCalledOnNullOrUndefined,
+                              isolate->factory()->NewStringFromAsciiChecked(
+                                  "set Object.prototype.__proto__")));
+  }
+
+  // 2. If Type(proto) is neither Object nor Null, return undefined.
+  Handle<Object> proto = args.at<Object>(1);
+  if (!proto->IsNull(isolate) && !proto->IsJSReceiver()) {
+    return isolate->heap()->undefined_value();
+  }
+
+  // 3. If Type(O) is not Object, return undefined.
+  if (!object->IsJSReceiver()) return isolate->heap()->undefined_value();
+  Handle<JSReceiver> receiver = Handle<JSReceiver>::cast(object);
+
+  // 4. Let status be ? O.[[SetPrototypeOf]](proto).
+  // 5. If status is false, throw a TypeError exception.
+  MAYBE_RETURN(
+      JSReceiver::SetPrototype(receiver, proto, true, Object::THROW_ON_ERROR),
+      isolate->heap()->exception());
+
+  // Return undefined.
+  return isolate->heap()->undefined_value();
+}
+
 // ES6 section 19.1.2.6 Object.getOwnPropertyDescriptor ( O, P )
 BUILTIN(ObjectGetOwnPropertyDescriptor) {
   HandleScope scope(isolate);