Revert "Fix language tests wrt. warnings."

tests/language/checked_setter_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 that implicit setters in checked mode do a type check.
 
 import "package:expect/expect.dart";
 
 class A {
   C c;
 }
 
 class B extends A {
 }
 
 class C {
 }
 
 var array = [new B()];
 
 main() {
   array[0].c = new C();
   bool inCheckedMode = false;
   try {
-    var i = 42;
-    String a = i;
+    String a = 42;
   } catch (e) {
     inCheckedMode = true;
   }
   if (inCheckedMode) {
     Expect.throws(() => array[0].c = new B(), (e) => e is TypeError);
   }
 }