Update assert to follow the spec.

compiler/lib/implementation/core.dart

 // Copyright (c) 2011, 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.
 
 class ConstHelper {
   static String getConstId(var o) native;
 
   static String getConstMapId(Map map) native {
     StringBuffer sb = new StringBuffer();
     sb.add("m");
@@ skipping 22 matching lines @@
   }
 
   static NoSuchMethodException createNoSuchMethodException(
       receiver, functionName, arguments) native {
     return new NoSuchMethodException(receiver, functionName, arguments);
   }
 
   static TypeError createTypeError(String srcType, String dstType) native {
     return new TypeError(srcType, dstType);
   }
+  
+  static AssertionError createAssertionError() native {
+    return new AssertionError();
+  }
 }
 
 class _CoreJsUtil {
   static Map _newMapLiteral() native {
     return new LinkedHashMap();
   }
 }