Roll Observatory packages and add a roll script

packages/code_transformers/lib/tests.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.
 
 /// Collection of utilities which are useful for creating unit tests for
 /// Barback transformers.
 library code_transformers.tests;
 
 import 'dart:async' show Future;
 import 'dart:io' show Platform;
@@ skipping 44 matching lines @@
     // If we cannot find the SDK dir, then assume this is being run from Dart's
     // source directory and this script is the main script.
     var segments = path.split(path.fromUri(Platform.script));
     var index = segments.indexOf('pkg');
     expect(index, greaterThan(0),
         reason: 'testingDartSdkDirectory is only supported in pkg/ tests');
     sdkDir = path.joinAll(segments.sublist(0, index)..add('sdk'));
   }
   return sdkDir;
 }