Skip native clauses when parsing directives.

pkg/front_end/lib/src/incremental/file_state.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.
 
 import 'dart:async';
 import 'dart:typed_data';
 
 import 'package:crypto/crypto.dart';
 import 'package:front_end/file_system.dart';
 import 'package:front_end/src/dependency_walker.dart' as graph;
+import 'package:front_end/src/fasta/parser/dart_vm_native.dart';
 import 'package:front_end/src/fasta/parser/top_level_parser.dart';
 import 'package:front_end/src/fasta/scanner.dart';
 import 'package:front_end/src/fasta/source/directive_listener.dart';
 import 'package:front_end/src/fasta/translate_uri.dart';
 import 'package:kernel/target/vm.dart';
 
 /// Information about a file being compiled, explicitly or implicitly.
 ///
 /// It provides a consistent view on its properties.
 ///
@@ skipping 87 matching lines @@
     } catch (_) {
       _content = new Uint8List(0);
       _exists = false;
     }
 
     // Compute the content hash.
     _contentHash = md5.convert(_content).bytes;
 
     // Parse directives.
     ScannerResult scannerResults = _scan();
-    var listener = new DirectiveListener();
+    var listener = new _DirectiveListenerWithNative();
     new TopLevelParser(listener).parseUnit(scannerResults.tokens);
 
     // Build the graph.
     _importedLibraries = <FileState>[];
     _exportedLibraries = <FileState>[];
     _partFiles = <FileState>[];
     await _addFileForRelativeUri(_importedLibraries, 'dart:core');
     for (String uri in listener.imports) {
       await _addFileForRelativeUri(_importedLibraries, uri);
     }
@@ skipping 120 matching lines @@
 
   @override
   String toString() {
     if (_isForVm) {
       return '[core + vm]';
     }
     return '[' + libraries.join(', ') + ']';
   }
 }
 
+/// [DirectiveListener] that skips native clauses.
+class _DirectiveListenerWithNative extends DirectiveListener {
+  @override
+  Token handleNativeClause(Token token) => skipNativeClause(token);
+}
+
 /// [FileSystemState] based implementation of [FileSystem].
 /// It provides a consistent view on the known file system state.
 class _FileSystemView implements FileSystem {
   final FileSystemState fsState;
 
   _FileSystemView(this.fsState);
 
   @override
   FileSystemEntity entityForUri(Uri uri) {
     FileState file = fsState._fileUriToFile[uri];
@@ skipping 70 matching lines @@
       node.isEvaluated = true;
       cycle.libraries.add(node.file);
     }
     topologicallySortedCycles.add(cycle);
   }
 
   _LibraryNode getNode(FileState file) {
     return nodesOfFiles.putIfAbsent(file, () => new _LibraryNode(this, file));
   }
 }