_visitTest should look through parentheses

lib/src/compiler/code_generator.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:collection' show HashMap, HashSet;
 import 'dart:math' show min, max;
 
 import 'package:analyzer/analyzer.dart' hide ConstantEvaluator;
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart' show Token, TokenType;
@@ skipping 4372 matching lines @@
   /// to give a more helpful message.
   // TODO(sra): When nullablility is available earlier, it would be cleaner to
   // build an input AST where the boolean conversion is a single AST node.
   JS.Expression _visitTest(Expression node) {
     JS.Expression finish(JS.Expression result) {
       return annotate(result, node);
     }
     if (node is PrefixExpression && node.operator.lexeme == '!') {
       return finish(js.call('!#', _visitTest(node.operand)));
     }
+    if (node is ParenthesizedExpression) {
+      return finish(_visitTest(node.expression));
+    }
     if (node is BinaryExpression) {
       JS.Expression shortCircuit(String code) {
         return finish(js.call(code,
             [_visitTest(node.leftOperand), _visitTest(node.rightOperand)]));
       }
       var op = node.operator.type.lexeme;
       if (op == '&&') return shortCircuit('# && #');
       if (op == '||') return shortCircuit('# || #');
     }
     // Offset 0 from start of file is syntactically impossible for normal code.
@@ skipping 258 matching lines @@
 }
 
 bool isLibraryPrefix(Expression node) =>
     node is SimpleIdentifier && node.staticElement is PrefixElement;
 
 LibraryElement _getLibrary(AnalysisContext c, String uri) =>
     c.computeLibraryElement(c.sourceFactory.forUri(uri));
 
 bool _isDartRuntime(LibraryElement l) =>
     l.isInSdk && l.source.uri.toString() == 'dart:_runtime';