Add support for building patched_sdk and platform.dill for dart2js:

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

 // Copyright (c) 2017, 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.
 
-/// Implements support for Dart VM native method bodies on this form:
+/// Implements support for Dart VM native method bodies of this form:
 ///
 ///     native STRING
 ///
 /// This support is kept separate from parser.dart as this isn't specified in
 /// the Dart Language Specification, also we hope to remove this syntax long
 /// term and replace it with annotations as in `dart2js`.
 library fasta.parser.dart_vm_native;
 
 import '../scanner/token.dart' show Token;
 
 import '../scanner/token_constants.dart' show STRING_TOKEN;
 
 import '../util/link.dart' show Link;
 
 import 'parser.dart' show optional;
 
 /// When parsing a Dart VM library file, we may encounter a native clause
 /// instead of a function body. This method skips such a clause.
 ///
 /// This method is designed to be called when encountering
 /// [ErrorKind.ExpectedBlockToSkip] in [Listener.handleUnrecoverableError].
-Token skipNativeClause(Token token) {
+Token skipVmNativeClause(Token token) {
   if (!optional("native", token)) return null;
   token = token.next;
   if (token.kind != STRING_TOKEN) return null;
   if (!optional(";", token.next)) return null;
   return token;
 }
 
 /// When parsing a Dart VM library file, we may encounter native getters like
 ///
 ///     int get length native "List_getLength";
 ///
 /// This will result in [identifiers] being
 ///
 ///     [";", '"List_getLength"', "native", "length", "get"]
 ///
 /// We need to remove '"List_getLength"' and "native" from that list.
 ///
 /// This method designed to be called from [Listener.handleMemberName].
 Link<Token> removeNativeClause(Link<Token> identifiers) {
   Link<Token> result = identifiers.tail;
   if (result.head.kind != STRING_TOKEN) return identifiers;
   result = result.tail;
   if (result.isEmpty) return identifiers;
   if (optional('native', result.head)) {
     return result.tail.prepend(identifiers.head);
   }
   return identifiers;
 }