Fix another closure/type variable error by using analyzeTypeVariables.

tests/language/issue14014_3_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 an is check on a function type involving type parameters
+// does not crash dart2js, when the is test is in the initializer list
+// of a constructor.
+
+class A<T> {
+  var f;
+  A(this.f);
+}
+
+typedef foo<T>(T a);
+
+class B<T> extends A<T> {
+  B({void f(T foo)}) : super(() => f is foo<T>);
+}
+
+main() {
+  var t = new B<int>(f: (int a) => 42);
+  if (!t.f()) {
+    throw 'Test failed';
+  }
+}