[parser] improve inferred function names for async arrow functions

src/parsing/func-name-inferrer.h

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_PARSING_FUNC_NAME_INFERRER_H_
 #define V8_PARSING_FUNC_NAME_INFERRER_H_
 
 #include "src/handles.h"
 #include "src/zone.h"
 
@@ skipping 53 matching lines @@
       funcs_to_infer_.Add(func_to_infer, zone());
     }
   }
 
   void RemoveLastFunction() {
     if (IsOpen() && !funcs_to_infer_.is_empty()) {
       funcs_to_infer_.RemoveLast();
     }
   }
 
+  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());
     if (!funcs_to_infer_.is_empty()) {
       InferFunctionsNames();
     }
   }
 
  private:
   enum NameType {
@@ skipping 34 matching lines @@
   Zone* zone_;
 
   DISALLOW_COPY_AND_ASSIGN(FuncNameInferrer);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_FUNC_NAME_INFERRER_H_