Roll Observatory packages and add a roll script

packages/csslib/lib/src/analyzer.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.
 
 part of csslib.parser;
 
 // TODO(terry): Add optimizing phase to remove duplicated selectors in the same
 //              selector group (e.g., .btn, .btn { color: red; }).  Also, look
 //              at simplifying selectors expressions too (much harder).
 // TODO(terry): Detect invalid directive usage.  All @imports must occur before
@@ skipping 995 matching lines @@
             isLastNone = false;
           }
         } else {
           isLastNone = simpleSeq.isCombinatorNone;
         }
       }
     }
     super.visitSelectorGroup(node);
   }
 }