[async-iteration] implement Async-from-Sync Iterator

src/builtins/builtins-async.h

Index: src/builtins/builtins-async.h
diff --git a/src/builtins/builtins-async.h b/src/builtins/builtins-async.h
index 9f5df6e04a39647b13924da4449dc78d4776b505..493eca06632d3eddcb8ec5c1694eb3c137f7cb90 100644
--- a/src/builtins/builtins-async.h
+++ b/src/builtins/builtins-async.h
@@ -15,6 +15,10 @@ class AsyncBuiltinsAssembler : public PromiseBuiltinsAssembler {
   explicit AsyncBuiltinsAssembler(CodeAssemblerState* state)
       : PromiseBuiltinsAssembler(state) {}
 
+  // Async Iterator
+  Node* AllocateAsyncIteratorValueUnwrapContext(Node* native_context,
+                                                Node* done);
+
  protected:
   typedef std::function<Node*(Node*)> NodeGenerator1;