Enable type inference when using mirrors.

tests/compiler/dart2js_extra/mirror_type_inference_field_test.dart

Index: tests/compiler/dart2js_extra/mirror_type_inference_field_test.dart
diff --git a/tests/compiler/dart2js_extra/mirror_type_inference_field_test.dart b/tests/compiler/dart2js_extra/mirror_type_inference_field_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..860d8c76ec8ed8aa16e4332636cfc2ab5fd00da9
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+++ b/tests/compiler/dart2js_extra/mirror_type_inference_field_test.dart
@@ -0,0 +1,20 @@
+// 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 type inference sees the possible modification of `fisk` from
+// the mirror system and not infers the value to be an integer.
+library test;
+
+@MirrorsUsed(targets: 'fisk', override: '*')
+import 'dart:mirrors';
+
+import 'package:expect/expect.dart';
+
+var fisk = 1;
+
+main() {
+  var lm = currentMirrorSystem().findLibrary(const Symbol('test')).single;
+  lm.setField(const Symbol('fisk'), 'hest');
+  Expect.isTrue(fisk is String);
+}