pkg/shelf: spelling fixes

lib/src/cascade.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.cascade;
 
 import 'handler.dart';
 import 'response.dart';
 import 'util.dart';
 
@@ skipping 20 matching lines @@
   /// the next handler.
   final _ShouldCascade _shouldCascade;
 
   final Cascade _parent;
   final Handler _handler;
 
   /// Creates a new, empty cascade.
   ///
   /// If [statusCodes] is passed, responses with those status codes are
   /// considered unacceptable. If [shouldCascade] is passed, responses for which
-  /// it returns `true` are considered unacceptale. [statusCode] and
+  /// it returns `true` are considered unacceptable. [statusCode] and
   /// [shouldCascade] may not both be passed.
   Cascade({Iterable<int> statusCodes, bool shouldCascade(Response response)})
       : _shouldCascade = _computeShouldCascade(statusCodes, shouldCascade),
         _parent = null,
         _handler = null {
     if (statusCodes != null && shouldCascade != null) {
       throw new ArgumentError("statusCodes and shouldCascade may not both be "
           "passed.");
     }
   }
@@ skipping 29 matching lines @@
 
 /// Computes the [Cascade._shouldCascade] function based on the user's
 /// parameters.
 Function _computeShouldCascade(
     Iterable<int> statusCodes, Function shouldCascade) {
   if (shouldCascade != null) return shouldCascade;
   if (statusCodes == null) statusCodes = [404, 405];
   statusCodes = statusCodes.toSet();
   return (response) => statusCodes.contains(response.statusCode);
 }