Allow direct access to type parameters from factory (issue 22700).

tests/language/regress_22700_test.dart

+// Copyright (c) 2015, 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.
+
+import "package:expect/expect.dart";
+
+class WrapT<T> {
+  Type get type => T;
+}
+
+printAndCheck(t) {
+  print(t);
+  Expect.equals(String, t);
+}
+
+class MyClass<T> {
+  factory MyClass.works() {
+    Type t = new WrapT<T>().type;
+    printAndCheck(t);
+  }
+
+  factory MyClass.works2() {
+    printAndCheck(T);
+  }
+}
+
+main() {
+  new MyClass<String>.works();
+  new MyClass<String>.works2();
+}