Handle parenthesized expression in type promotion.

tests/language/type_promotion_parameter_test.dart

Index: tests/language/type_promotion_parameter_test.dart
diff --git a/tests/language/type_promotion_parameter_test.dart b/tests/language/type_promotion_parameter_test.dart
index b390ede076b05cdaa03314fcf94981998c532139..6fe7eccc0963a7a70622829add686c01173ba99b 100644
--- a/tests/language/type_promotion_parameter_test.dart
+++ b/tests/language/type_promotion_parameter_test.dart
@@ -190,8 +190,14 @@ void test(A a) {
   }
   if ((a is B)) {
     print(a.a);
-    print(a.b); /// 53: static type warning
+    print(a.b);
     print(a.c); /// 54: static type warning
     print(a.d); /// 55: static type warning
   }
+  if ((a is B && (a) is C) && a is B) {
+    print(a.a);
+    print(a.b);
+    print(a.c);
+    print(a.d); /// 56: static type warning
+  }
 }