[kernel] Make fasta call a new constructor on FallThroughError

sdk/lib/core/errors.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.
 
 part of dart.core;
 
 /**
  * Error objects thrown in the case of a program failure.
  *
  * An `Error` object represents a program failure that the programmer
@@ skipping 393 matching lines @@
 /**
  * Error thrown when control reaches the end of a switch case.
  *
  * The Dart specification requires this error to be thrown when
  * control reaches the end of a switch case (except the last case
  * of a switch) without meeting a break or similar end of the control
  * flow.
  */
 class FallThroughError extends Error {
   FallThroughError();
+  external FallThroughError._create(String url, int line);
 
   external String toString();
 }
 
 /**
  * Error thrown when trying to instantiate an abstract class.
  */
 class AbstractClassInstantiationError extends Error {
   final String _className;
   AbstractClassInstantiationError(String className) : _className = className;
@@ skipping 134 matching lines @@
       : "Reading static variable '$variableName' during its initialization";
 }
 
 /// Used by Fasta to throw a compile-time error in a way that is compatible
 /// with compile-time constant evaluation.
 class _ConstantExpressionError {
   const _ConstantExpressionError();
 
   external _throw(error);
 }