Switch on null-aware operators by default in analyzer.

pkg/analyzer/lib/src/task/dart.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 analyzer.src.task.dart;
 
 import 'dart:collection';
 
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/generated/ast.dart';
@@ skipping 3097 matching lines @@
         throw new AnalysisException(
             'Cannot scan scripts with multiple fragments');
       }
       ScriptFragment fragment = fragments[0];
 
       Scanner scanner = new Scanner(source,
           new SubSequenceReader(fragment.content, fragment.offset),
           errorListener);
       scanner.setSourceStart(fragment.line, fragment.column);
       scanner.preserveComments = context.analysisOptions.preserveComments;
-      scanner.enableNullAwareOperators =
-          context.analysisOptions.enableNullAwareOperators;
 
       outputs[TOKEN_STREAM] = scanner.tokenize();
       outputs[LINE_INFO] = new LineInfo(scanner.lineStarts);
       outputs[SCAN_ERRORS] = removeDuplicateErrors(errorListener.errors);
     } else if (target is Source) {
       String content = getRequiredInput(CONTENT_INPUT_NAME);
 
       Scanner scanner =
           new Scanner(source, new CharSequenceReader(content), errorListener);
       scanner.preserveComments = context.analysisOptions.preserveComments;
-      scanner.enableNullAwareOperators =
-          context.analysisOptions.enableNullAwareOperators;
 
       outputs[TOKEN_STREAM] = scanner.tokenize();
       outputs[LINE_INFO] = new LineInfo(scanner.lineStarts);
       outputs[SCAN_ERRORS] = removeDuplicateErrors(errorListener.errors);
     } else {
       throw new AnalysisException(
           'Cannot scan Dart code from a ${target.runtimeType}');
     }
   }
 
@@ skipping 264 matching lines @@
 
   @override
   bool moveNext() {
     if (_newSources.isEmpty) {
       return false;
     }
     currentTarget = _newSources.removeLast();
     return true;
   }
 }