Support conditional directives in the options file.

pkg/analyzer/lib/src/generated/incremental_resolver.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 analyzer.src.generated.incremental_resolver;
 
 import 'dart:collection';
 import 'dart:math' as math;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 1603 matching lines @@
     return false;
   }
 
   CompilationUnit _parseUnit(String code) {
     LoggingTimer timer = logger.startTimer();
     try {
       Token token = _scan(code);
       RecordingErrorListener errorListener = new RecordingErrorListener();
       Parser parser = new Parser(_unitSource, errorListener);
       AnalysisOptions options = _unitElement.context.analysisOptions;
+      parser.parseConditionalDirectives = options.enableConditionalDirectives;
       parser.parseGenericMethods = options.enableGenericMethods;
       CompilationUnit unit = parser.parseCompilationUnit(token);
       _newParseErrors = errorListener.errors;
       return unit;
     } finally {
       timer.stop('parse');
     }
   }
 
   /**
@@ skipping 567 matching lines @@
   @override
   String toString() => name;
 }
 
 class _TokenPair {
   final _TokenDifferenceKind kind;
   final Token oldToken;
   final Token newToken;
   _TokenPair(this.kind, this.oldToken, this.newToken);
 }