Add a (public) utility method to clean-up code

pkg/analyzer/lib/dart/ast/ast.dart

Index: pkg/analyzer/lib/dart/ast/ast.dart
diff --git a/pkg/analyzer/lib/dart/ast/ast.dart b/pkg/analyzer/lib/dart/ast/ast.dart
index 9e5bca2277dd345ed29ab0dbc8a43235f0bac2d0..6fa9188a337b24e569aadfeb713848b31ea3d416 100644
--- a/pkg/analyzer/lib/dart/ast/ast.dart
+++ b/pkg/analyzer/lib/dart/ast/ast.dart
@@ -3038,6 +3038,13 @@ abstract class Expression extends AstNode {
    * Set the static type of this expression to the given [type].
    */
   void set staticType(DartType type);
+
+  /**
+   * If this expression is a parenthesized expression, return the result of
+   * unwrapping the expression inside the parentheses. Otherwise, return this
+   * expression.
+   */
+  Expression get unParenthesized;
 }
 
 /**