pkg/shelf: formatted code

lib/src/hijack_exception.dart

 // Copyright (c) 2014, 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 shelf.hijack_exception;
 
 /// An exception used to indicate that a request has been hijacked.
 ///
 /// This shouldn't be captured by any code other than the Shelf adapter that
 /// created the hijackable request. Middleware that captures exceptions should
 /// make sure to pass on HijackExceptions.
 ///
 /// See also [Request.hijack].
 class HijackException {
   const HijackException();
 
   String toString() =>
       "A shelf request's underlying data stream was hijacked.\n"
       "This exception is used for control flow and should only be handled by a "
-        "Shelf adapter.";
+      "Shelf adapter.";
 }