Don't hide interceptors in mirrors.

sdk/lib/_internal/lib/interceptors.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.
 
 library _interceptors;
 
 import 'dart:collection';
 import 'dart:_internal' hide Symbol;
 import "dart:_internal" as _symbol_dev show Symbol;
 import 'dart:_js_helper' show allMatchesInStringUnchecked,
@@ skipping 311 matching lines @@
 class JSNull extends Interceptor implements Null {
   const JSNull();
 
   bool operator ==(other) => identical(null, other);
 
   // Note: if you change this, also change the function [S].
   String toString() => 'null';
 
   int get hashCode => 0;
 
+  // The spec guarantees that `null` is the singleton instance of the `Null`
+  // class. In the mirrors library we also have to patch the `type` getter to
+  // special case `null`.
   Type get runtimeType => Null;
+
+  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 }
 
 /**
  * The supertype for JSString and JSArray. Used by the backend as to
  * have a type mask that contains the objects that we can use the
  * native JS [] operator and length on.
  */
 abstract class JSIndexable {
   int get length;
   operator[](int index);
@@ skipping 41 matching lines @@
 }
 
 
 /**
  * Interceptor for unclassified JavaScript objects, typically objects with a
  * non-trivial prototype chain.
  */
 class UnknownJavaScriptObject extends JavaScriptObject {
   const UnknownJavaScriptObject();
 }