Unify paren handling in (Pre)Parser::ParseExpressionOrLabelledStatement.

src/ast.h

Index: src/ast.h
diff --git a/src/ast.h b/src/ast.h
index 2b33820f9e1ca029a190157adce3a8a583af995b..2b04599ae286906aea109eff90d414fb2313b206 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -351,6 +351,10 @@ class Expression : public AstNode {
   // True if we can prove that the expression is the undefined literal.
   bool IsUndefinedLiteral(Isolate* isolate);
 
+  bool IsIdentifier();
+
+  bool IsIdentifierNamed(String* name);
+
   // Expression type bounds
   Bounds bounds() { return bounds_; }
   void set_bounds(Bounds bounds) { bounds_ = bounds; }