Add optional message to assert in Dart2js.

pkg/compiler/lib/src/common/registry.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 dart2js.common.registry;
 
 import '../dart_types.dart' show
   InterfaceType;
 import '../elements/elements.dart' show
   Element,
@@ skipping 15 matching lines @@
 
   void registerDynamicGetter(UniverseSelector selector);
 
   void registerDynamicSetter(UniverseSelector selector);
 
   void registerStaticInvocation(Element element);
 
   void registerInstantiation(InterfaceType type);
 
   void registerGetOfStaticFunction(FunctionElement element);
+
+  void registerAssert(bool hasMessage);
 }