add support for native methods in class

pkg/front_end/lib/src/fasta/parser/parser.dart

 // Copyright (c) 2012, 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 fasta.parser.parser;
 
 import '../fasta_codes.dart' show Code, Message, Template;
 
 import '../fasta_codes.dart' as fasta;
 
@@ skipping 2388 matching lines @@
       isGetter = optional("get", getOrSet);
       listener.handleNoTypeVariables(token);
     }
     checkFormals(isGetter, name, token);
     token = parseFormalParametersOpt(
         token,
         staticModifier != null
             ? MemberKind.StaticMethod
             : MemberKind.NonStaticMethod);
     token = parseInitializersOpt(token);
+
+    Token nativeToken;
+    if (optional('native', token)) {
+      nativeToken = token;
+      token = parseNativeClause(nativeToken);

[ahe, 2017/08/25 09:05:40]

I think the problem is how functions bodies are being skipped in
ClassMemberParser (and thus DietParser). 

If I'm right, the solution should be to move this logic to parseFunctionBody and
update skipFunctionBody to generate the native event.

+    }
+
     AsyncModifier savedAsyncModifier = asyncState;
     Token asyncToken = token;
     token = parseAsyncModifier(token);
     if (getOrSet != null && !inPlainSync && optional("set", getOrSet)) {
       reportRecoverableError(asyncToken, fasta.messageSetterNotSync);
     }
     if (optional('=', token)) {
       token = parseRedirectingFactoryBody(token);
     } else {
       token = parseFunctionBody(
-          token, false, staticModifier == null || externalModifier != null);
+          token,
+          false,
+          staticModifier == null ||
+              externalModifier != null ||
+              nativeToken != null);
     }
     asyncState = savedAsyncModifier;
-    listener.endMethod(getOrSet, start, token);
+    listener.endMethod(getOrSet, start, nativeToken, token);
     return token.next;
   }
 
   Token parseFactoryMethod(Token token) {
     assert(isFactoryDeclaration(token));
     Token start = token;
     bool isExternal = false;
     int modifierCount = 0;
     while (isModifier(token)) {
       if (optional('external', token)) {
@@ skipping 1704 matching lines @@
   }
 
   Token reportUnexpectedToken(Token token) {
     return reportUnrecoverableErrorWithToken(
         token, fasta.templateUnexpectedToken);
   }
 }
 
 // TODO(ahe): Remove when analyzer supports generalized function syntax.
 typedef _MessageWithArgument<T> = Message Function(T);