Roll Observatory packages and add a roll script

packages/csslib/lib/src/tree_printer.dart

 // Copyright (c) 2013, 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.visitor;
 
 // TODO(terry): Enable class for debug only; when conditional imports enabled.
 
 /** Helper function to dump the CSS AST. */
 String treeToDebugString(StyleSheet styleSheet, [bool useSpan = false]) {
@@ skipping 538 matching lines @@
   }
 
   void visitPaddingExpression(PaddingExpression node) {
     heading('Dart Style PaddingExpression', node);
   }
 
   void visitWidthExpression(WidthExpression node) {
     heading('Dart Style WidthExpression', node);
   }
 }