Remove some exceptions from mock.dart.

lib/compiler/implementation/lib/mock.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.
 
 // Mocks of things that Leg cannot read directly.
 
 // TODO(ahe): Remove this file.
 
-// TODO(ahe): VM specfic exception?
-class InternalError {
-  const InternalError(this._msg);
-  String toString() => "InternalError: '${_msg}'";
-  final String _msg;
-}
-
-// TODO(ahe): VM specfic exception?
-class StaticResolutionException implements Exception {}
-
 void assert(condition) {
   if (condition is Function) condition = condition();
   if (!condition) throw new AssertionError();
 }
 
 // TODO(ahe): Not sure ByteArray belongs in the core library.
 interface Uint8List extends List default _InternalByteArray {
   Uint8List(int length);
 }
 
 class _InternalByteArray {
   factory Uint8List(int length) {
     throw new UnsupportedOperationException("new Uint8List($length)");
   }
 }