Add regression tests for two issues (7525, 7513).

tests/language/issue7525_test.dart

+// Copyright (c) 2012, 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.
+
+// Regression test for issue 7525.
+
+foo() {
+  var ol = <int>[2];
+  (ol as List<int>)[0];
+  int x = (ol as List<int>)[0];
+  return x;
+}
+
+main() {
+  for (int i = 0; i < 5000; i++) {
+    foo();
+  }
+  Expect.equals(2, foo());
+}