Change StackOverflowException to be an Error.

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.
 
 class Error {
   const Error();
 }
 
 class AssertionError implements Error {
 }
 
 class TypeError implements AssertionError {
 }
 
 class CastError implements Error {
 }
 
 /**
  * Error thrown when a function is passed an unacceptable argument.
- */
-class ArgumentError implements Error {
+ */class ArgumentError implements Error {
   final message;
 
   /** The [message] describes the erroneous argument. */
   const ArgumentError([this.message = ""]);
 
   String toString() {
     if (message != null) {
       return "Illegal argument(s): $message";
     }
     return "Illegal argument(s)";
   }
 }
 
 /**
  * Temporary backwards compatibility class.
  *
  * Removed when users have had time to change to using [ArgumentError].
  */
 class IllegalArgumentException extends ArgumentError {
   const IllegalArgumentException([argument = ""]) : super(argument);
 }
 
-
+/**
+ * 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 implements Error {
   const FallThroughError();
 }
 
 class AbstractClassInstantiationError implements Error {
   final String _className;
   const AbstractClassInstantiationError(String this._className);
   String toString() => "Cannot instantiate abstract class: '$_className'";
 }
 
@@ skipping 69 matching lines @@
         .replaceAll('"',  '$backslash"');
       return '"$escaped"';
     }
     return _objectToString(object);
   }
 
   external static String _objectToString(Object object);
 }
 
 
-class OutOfMemoryError implements Exception {
+class OutOfMemoryError implements Error {
   const OutOfMemoryError();
   String toString() => "Out of Memory";
 }
+
+class StackOverflowError implements Error {
+  const StackOverflowError();
+  String toString() => "Stack Overflow";
+}