Handle parenthesized expression in type promotion.

tests/language/type_promotion_logical_and_test.dart

 // Copyright (c) 2013, 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.
 
 // Test type promotion of locals potentially mutated.
 
 class A {
   var a = true;
 }
 class B extends A {
@@ skipping 15 matching lines @@
 void main() {
   A a = new E();
   var b;
   if (a is D && ((a = new D()) != null)) {
     b = a.d; /// 01: static type warning
   }
   if (a is D && (b = a.d)) {
     b = a.d; /// 02: static type warning
     a = null;
   }
+  if ((((a) is D) && (b = (a).d))) {
+    b = a.d; /// 03: static type warning
+    a = null;
+  }
   if (f(a = null) && a is D) {
     b = a.d;
   }
 }
 
 bool f(x) => true;