Fix mirrors to keep typedef as scope class of function types (fixes #26187).

tests/lib/mirrors/regress_26187_test.dart

+// Copyright (c) 2016, 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 'dart:mirrors';
+import 'package:expect/expect.dart';
+
+class A {
+  const A();
+}
+
+class B {
+  const B();
+}
+
+typedef void f(@A() int, String);
+
+typedef void g(@B() int, String);
+
+main() {
+  ParameterMirror fParamMirror = (reflectType(f) as TypedefMirror).referent.parameters[0];
+  ParameterMirror gParamMirror = (reflectType(g) as TypedefMirror).referent.parameters[0];
+  Expect.equals('.A', MirrorSystem.getName(fParamMirror.metadata[0].type.qualifiedName));
+  Expect.equals('.B', MirrorSystem.getName(gParamMirror.metadata[0].type.qualifiedName));
+}