WIP [esnext] implement async iteration proposal

src/code-stub-assembler.cc

Index: src/code-stub-assembler.cc
diff --git a/src/code-stub-assembler.cc b/src/code-stub-assembler.cc
index 1fb8a2152ee587eb5176e6c46707fbf7f679efd5..385c09d662e71f19dfc7e2b18c84772b99e3368f 100644
--- a/src/code-stub-assembler.cc
+++ b/src/code-stub-assembler.cc
@@ -8174,6 +8174,23 @@ Node* CodeStubAssembler::AllocateJSArrayIterator(Node* array, Node* array_map,
   return iterator;
 }
 
+Node* CodeStubAssembler::AllocateJSIteratorResult(Node* context, Node* value,
+                                                  Node* done) {
+  Node* const iter_result = Allocate(JSIteratorResult::kSize);
+  Node* const map = LoadContextElement(LoadNativeContext(context),
+                                       Context::ITERATOR_RESULT_MAP_INDEX);
+  StoreMapNoWriteBarrier(iter_result, map);
+  StoreObjectFieldRoot(iter_result, JSIteratorResult::kPropertiesOffset,
+                       Heap::kEmptyFixedArrayRootIndex);
+  StoreObjectFieldRoot(iter_result, JSIteratorResult::kElementsOffset,
+                       Heap::kEmptyFixedArrayRootIndex);
+  StoreObjectFieldNoWriteBarrier(iter_result, JSIteratorResult::kValueOffset,
+                                 value);
+  StoreObjectFieldNoWriteBarrier(iter_result, JSIteratorResult::kDoneOffset,
+                                 done);
+  return iter_result;
+}
+
 Node* CodeStubAssembler::IsDetachedBuffer(Node* buffer) {
   CSA_ASSERT(this, HasInstanceType(buffer, JS_ARRAY_BUFFER_TYPE));