Pull args, intl, logging, shelf, and source_maps out of the SDK.

pkg/shelf/lib/src/pipeline.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.pipeline;
-
-import 'handler.dart';
-import 'middleware.dart';
-
-/// A helper that makes it easy to compose a set of [Middleware] and a
-/// [Handler].
-///
-///     var handler = const Pipeline()
-///         .addMiddleware(loggingMiddleware)
-///         .addMiddleware(cachingMiddleware)
-///         .addHandler(application);
-class Pipeline {
-  final Pipeline _parent;
-  final Middleware _middleware;
-
-  const Pipeline()
-      : _middleware = null,
-        _parent = null;
-
-  Pipeline._(this._middleware, this._parent);
-
-  /// Returns a new [Pipeline] with [middleware] added to the existing set of
-  /// [Middleware].
-  ///
-  /// [middleware] will be the last [Middleware] to process a request and
-  /// the first to process a response.
-  Pipeline addMiddleware(Middleware middleware) =>
-      new Pipeline._(middleware, this);
-
-  /// Returns a new [Handler] with [handler] as the final processor of a
-  /// [Request] if all of the middleware in the pipeline have passed the request
-  /// through.
-  Handler addHandler(Handler handler) {
-    if (_middleware == null) return handler;
-    return _parent.addHandler(_middleware(handler));
-  }
-
-  /// Exposes this pipeline of [Middleware] as a single middleware instance.
-  Middleware get middleware => addHandler;
-}