Implement fall-through errors.

lib/kernel.dart

 // Copyright (c) 2016, 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.md file.
 
 library rasta.kernel;
 
 import 'dart:async' show
     Future;
 
 import 'dart:collection' show
@@ skipping 664 matching lines @@
     return getDartCoreMethod('_unresolvedSuperSetterError');
   }
 
   ir.Procedure getUnresolvedSuperMethodBuilder() {
     return getDartCoreMethod('_unresolvedSuperMethodError');
   }
 
   ir.Procedure getGenericNoSuchMethodBuilder() {
     return getDartCoreMethod('_genericNoSuchMethod');
   }
+
+  ir.Procedure getFallThroughErrorBuilder() {
+    return getDartCoreMethod('_fallThroughError');
+  }
 }
 
 class ConstructorTarget {
   final ConstructorElement element;
   final DartType type;
 
   ConstructorTarget(this.element, this.type);
 
   String toString() => "ConstructorTarget($element, $type)";
 }