Remove support for Javascript warnings in the VM.

runtime/lib/errors_patch.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.
 
 import 'dart:_internal' as internal;
 import 'dart:convert' show JSON;
 
 patch class Error {
   /* patch */ static String _objectToString(Object object) {
     return Object._toString(object);
@@ skipping 344 matching lines @@
       msg_buf.write(
           "NoSuchMethodError: incorrect number of arguments passed to "
           "method named '$memberName'\n"
           "Receiver: $receiver_str\n"
           "Tried calling: $memberName($actualParameters)\n"
           "Found: $memberName($formalParameters)");
     }
     return msg_buf.toString();
   }
 }
-
-class _JavascriptIntegerOverflowError extends Error {
-  final Object _value;
-
-  _JavascriptIntegerOverflowError(this._value);
-  String toString() => "Javascript Integer Overflow: $_value";
-}
-
-class _JavascriptCompatibilityError extends Error {
-  final String _msg;
-
-  _JavascriptCompatibilityError(this._msg);
-  String toString() => "Javascript Compatibility Error: $_msg";
-}
-