Issue 21373. Fix for removing line info in case of exception (causes NPE in outline computer).

pkg/analyzer/lib/src/generated/engine.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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine;
 
 import 'dart:collection';
@@ skipping 1992 matching lines @@
               _recordElementData(
                   dartEntry,
                   library.libraryElement,
                   librarySource, htmlSource);
             }
             _cache.storedAst(source);
           } else {
             dartEntry.recordResolutionErrorInLibrary(
                 librarySource,
                 thrownException);
-            _cache.remove(source);
           }
           if (source != librarySource) {
             _workManager.add(source, SourcePriority.PRIORITY_PART);
           }
           ChangeNoticeImpl notice = _getNotice(source);
           notice.compilationUnit = unit;
           notice.setErrors(dartEntry.allErrors, lineInfo);
         }
       }
     }
@@ skipping 11456 matching lines @@
     _index++;
     if (_index >= _manager._workQueues[_queueIndex].length) {
       _index = 0;
       _queueIndex++;
       while (_queueIndex < _manager._workQueues.length && _manager._workQueues[_queueIndex].isEmpty) {
         _queueIndex++;
       }
     }
   }
 }