Teach analyzer parser to handle native const factories/const constructors.

pkg/analyzer/lib/src/generated/parser.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.parser;
 
 import 'dart:collection';
 import "dart:math" as math;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 6234 matching lines @@
       if (factoryKeyword == null) {
         _reportErrorForNode(
             ParserErrorCode.REDIRECTION_IN_NON_FACTORY_CONSTRUCTOR,
             redirectedConstructor);
       }
     } else {
       body =
           parseFunctionBody(true, ParserErrorCode.MISSING_FUNCTION_BODY, false);
       if (constKeyword != null &&
           factoryKeyword != null &&
-          externalKeyword == null) {
+          externalKeyword == null &&
+          body is! NativeFunctionBody) {
         _reportErrorForToken(ParserErrorCode.CONST_FACTORY, factoryKeyword);
       } else if (body is EmptyFunctionBody) {
         if (factoryKeyword != null &&
             externalKeyword == null &&
             _parseFunctionBodies) {
           _reportErrorForToken(
               ParserErrorCode.FACTORY_WITHOUT_BODY, factoryKeyword);
         }
       } else {
-        if (constKeyword != null) {
+        if (constKeyword != null && body is! NativeFunctionBody) {
           _reportErrorForNode(
               ParserErrorCode.CONST_CONSTRUCTOR_WITH_BODY, body);
         } else if (externalKeyword != null) {
           _reportErrorForNode(
               ParserErrorCode.EXTERNAL_CONSTRUCTOR_WITH_BODY, body);
         } else if (!bodyAllowed) {
           _reportErrorForNode(
               ParserErrorCode.REDIRECTING_CONSTRUCTOR_WITH_BODY, body);
         }
       }
@@ skipping 1823 matching lines @@
    */
   Parser_SyntheticKeywordToken(Keyword keyword, int offset)
       : super(keyword, offset);
 
   @override
   int get length => 0;
 
   @override
   Token copy() => new Parser_SyntheticKeywordToken(keyword, offset);
 }