Roll Observatory packages and add a roll script

packages/dart_style/lib/src/line_splitting/solve_state_queue.dart

 // Copyright (c) 2015, 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 dart_style.src.line_splitting.solve_state_queue;
 
 import 'line_splitter.dart';
 import 'solve_state.dart';
 
 /// A priority queue of [SolveStates] to consider while line splitting.
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       if (comparison > 0) {
         _queue[index] = child;
         index = leftChildIndex;
       }
     }
 
     _queue[index] = element;
   }
 }