remove generated_sdk from checked in code

test/generated_sdk/lib/async/async_error.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.async;
-
-_invokeErrorHandler(Function errorHandler,
-                    Object error, StackTrace stackTrace) {
-  if (errorHandler is ZoneBinaryCallback) {
-    return errorHandler(error, stackTrace);
-  } else {
-    return errorHandler(error);
-  }
-}
-
-Function _registerErrorHandler(Function errorHandler, Zone zone) {
-  if (errorHandler is ZoneBinaryCallback) {
-    return zone.registerBinaryCallback(errorHandler);
-  } else {
-    return zone.registerUnaryCallback(errorHandler);
-  }
-}
-
-class _UncaughtAsyncError extends AsyncError {
-  _UncaughtAsyncError(error, StackTrace stackTrace)
-      : super(error, _getBestStackTrace(error, stackTrace));
-
-  static StackTrace _getBestStackTrace(error, StackTrace stackTrace) {
-    if (stackTrace != null) return stackTrace;
-    if (error is Error) {
-      return error.stackTrace;
-    }
-    return null;
-  }
-
-  String toString() {
-    String result = "Uncaught Error: ${error}";
-
-    if (stackTrace != null) {
-      result += "\nStack Trace:\n$stackTrace";
-    }
-    return result;
-  }
-}