Roll Observatory packages and add a roll script

packages/string_scanner/lib/src/line_scanner.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.
 
 library string_scanner.line_scanner;
 
 import 'package:charcode/ascii.dart';
 
 import 'string_scanner.dart';
 
@@ skipping 107 matching lines @@
   final int position;
 
   /// The zero-based line number of the scanner in this state.
   final int line;
 
   /// The zero-based column number of the scanner in this state.
   final int column;
 
   LineScannerState._(this._scanner, this.position, this.line, this.column);
 }