[parser] improve inferred function names for async arrow functions

src/parsing/parser-base.h

Index: src/parsing/parser-base.h
diff --git a/src/parsing/parser-base.h b/src/parsing/parser-base.h
index c7e4daf97c2b555056c1e17d9d7d78d09df19f0f..f6c2c640abb146c6355c51f9457a7ea4aac8100d 100644
--- a/src/parsing/parser-base.h
+++ b/src/parsing/parser-base.h
@@ -2325,8 +2325,13 @@ ParserBase<Traits>::ParseAssignmentExpression(bool accept_IN,
     // async Identifier => AsyncConciseBody
     IdentifierT name =
         ParseAndClassifyIdentifier(&arrow_formals_classifier, CHECK_OK);
-    expression = this->ExpressionFromIdentifier(name, position(),
-                                                scanner()->location().end_pos);
+    expression = this->ExpressionFromIdentifier(
+        name, position(), scanner()->location().end_pos, InferName::No);
+    if (fni_) {
+      // Remove `async` keyword from inferred name stack.
+      DCHECK_EQ(fni_->LastName(), ast_value_factory()->async_string());
+      fni_->RemoveLastName();
+    }
   }
 
   if (peek() == Token::ARROW) {
@@ -2883,9 +2888,13 @@ ParserBase<Traits>::ParseLeftHandSideExpression(
         Scanner::Location spread_pos;
         typename Traits::Type::ExpressionList args;
         if (V8_UNLIKELY(is_async)) {
+          int async_index = fni_ ? fni_->LastNameIndex() : -1;
           ExpressionClassifier async_classifier(this);
           args = ParseArguments(&spread_pos, true, &async_classifier, CHECK_OK);
           if (peek() == Token::ARROW) {
+            if (fni_) {
+              fni_->RemoveNameAtIndex(async_index);

[Dan Ehrenberg, 2016/08/12 18:16:40]

DCHECK that it is removing async? Maybe the fni API should be 'remove async at'
and do the DCHECK there, rather than exposing LastName() just for the sake of
the DCHECK in the caller.

+            }
             ValidateBindingPattern(&async_classifier, CHECK_OK);
             if (!async_classifier.is_valid_async_arrow_formal_parameters()) {
               ReportClassifierError(