Fix type test elimination of function types using static type propagation in

tests/language/function_type_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.
+// Dart test for a function type test that cannot be eliminated at compile time.
+
+isCheckedMode() {
+  try {
+    var i = 1;
+    String s = i;
+    return false;
+  } catch(var e) {
+    return true;
+  }
+}
+
+typedef FList(List l);
+typedef FListInt(List<int> l);
+
+FList f() {
+  return (List<String> l) => null; // Type of function is a subtype of FList.
+}
+
+main() {
+  bool got_type_error = false;
+  try {
+    // Static result type of f(), i.e. FList, is a subtype of FListInt.
+    // However, run time type of returned function is not a subtype of FListInt.
+    // Run time type check should not be eliminated.
+    FListInt fli = f();
+  } catch (TypeError error) {
+    got_type_error = true;
+  }
+  // Type error expected in checked mode only.
+  Expect.isTrue(got_type_error == isCheckedMode());
+}