Add logging system to pub and sprinkle some logging in.

pkg/http/lib/src/base_request.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.
 
 library base_request;
 
 import 'dart:io';
 import 'dart:isolate';
 import 'dart:uri';
 
@@ skipping 107 matching lines @@
 
       return response;
     });
   }
 
   /// Throws an error if this request has been finalized.
   void _checkFinalized() {
     if (!finalized) return;
     throw new StateError("Can't modify a finalized Request.");
   }
+
+  String toString() => "$method $url";
 }