[parser] improve inferred function names for async arrow functions

src/parsing/func-name-inferrer.h

Index: src/parsing/func-name-inferrer.h
diff --git a/src/parsing/func-name-inferrer.h b/src/parsing/func-name-inferrer.h
index ba38ffeb241c348ab8e285a842b08e5f12590615..97fee30cdb2b15e4f11ba4a50789cdbee513019b 100644
--- a/src/parsing/func-name-inferrer.h
+++ b/src/parsing/func-name-inferrer.h
@@ -71,6 +71,19 @@ class FuncNameInferrer : public ZoneObject {
     }
   }
 
+  int LastNameIndex() const { return this->names_stack_.length() - 1; }
+
+  void RemoveNameAtIndex(int index) {
+    DCHECK(index >= 0);
+    DCHECK(index < names_stack_.length());
+    names_stack_.Remove(index);
+  }
+
+  void RemoveLastName() {
+    DCHECK(names_stack_.length() > 0);
+    RemoveNameAtIndex(names_stack_.length() - 1);
+  }
+
   // Infers a function name and leaves names collection state.
   void Infer() {
     DCHECK(IsOpen());