Roll Observatory packages and add a roll script

packages/analyzer/lib/instrumentation/file_instrumentation.dart

 // Copyright (c) 2015, 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 file_instrumentation;
 
 import 'dart:io';
 
 import 'package:analyzer/instrumentation/instrumentation.dart';
 
@@ skipping 17 matching lines @@
   void logWithPriority(String message) {
     log(message);
   }
 
   @override
   void shutdown() {
     _sink.close();
     _sink = null;
   }
 }