Roll Observatory packages and add a roll script

packages/csslib/lib/src/tokenizer_base.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.
 // Generated by scripts/tokenizer_gen.py.
 
 part of csslib.parser;
 
 /** Tokenizer state to support look ahead for Less' nested selectors. */
 class TokenizerState {
   final int index;
@@ skipping 398 matching lines @@
 
   Token finishDot() {
     if (TokenizerHelpers.isDigit(_peekChar())) {
       eatDigits();
       return finishNumberExtra(TokenKind.DOUBLE);
     } else {
       return _finishToken(TokenKind.DOT);
     }
   }
 }