Heuristic for eager parsing works for async functions

The heuristic checks for "(function", and now it also checks for
"(async function".

BUG=v8:4230

Review-Url: https://codereview.chromium.org/2682173005
Cr-Commit-Position: refs/heads/master@{#43120}

src/parsing/parser-base.h

@@ -1845,7 +1845,8 @@ typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParsePrimaryExpression(
       }
       // Heuristically try to detect immediately called functions before
       // seeing the call parentheses.
-      if (peek() == Token::FUNCTION) {
+      if (peek() == Token::FUNCTION ||
+          (peek() == Token::ASYNC && PeekAhead() == Token::FUNCTION)) {
         function_state_->set_next_function_is_likely_called();
       }
       ExpressionT expr = ParseExpressionCoverGrammar(true, CHECK_OK);

test/test262/test262.status

@@ -407,7 +407,6 @@
   # PreParser doesn't produce early errors
   # https://bugs.chromium.org/p/v8/issues/detail?id=2728
   'language/expressions/async-arrow-function/early-errors-arrow-formals-body-duplicate': [FAIL],
-  'language/expressions/async-function/early-errors-expression-formals-body-duplicate': [FAIL],
   'language/expressions/object/method-definition/generator-param-redecl-const': [FAIL],
   'language/expressions/object/method-definition/generator-param-redecl-let': [FAIL],
   'language/expressions/object/method-definition/name-param-redecl': [FAIL],