Stop running pub get at gclient sync time and fix build bugs

mojo/public/dart/third_party/shelf/lib/src/handler.dart

Index: mojo/public/dart/third_party/shelf/lib/src/handler.dart
diff --git a/mojo/public/dart/third_party/shelf/lib/src/handler.dart b/mojo/public/dart/third_party/shelf/lib/src/handler.dart
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+// 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.typedef;
+
+import 'request.dart';
+
+/// The signature of a function which handles a [Request].
+///
+/// A [Handler] may receive a request directly from an HTTP server or it
+/// may be composed as part of a larger application.
+///
+/// Should return [Response] or [Future<Response>].
+//TODO(kevmoo): provide a more detailed explanation.
+typedef Handler(Request request);