improve fasta export directive recovery

pkg/compiler/lib/src/parser/node_listener.dart

 // Copyright (c) 2015, 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 dart2js.parser.node_listener;
 
 import 'package:front_end/src/fasta/parser.dart'
     show FormalParameterKind, IdentifierContext, MemberKind;
 import 'package:front_end/src/fasta/scanner.dart' show Token;
 import 'package:front_end/src/scanner/token.dart' show TokenType;
@@ skipping 119 matching lines @@
     // TODO(sigmund): consider moving metadata into each declaration
     // element instead.
     Node node = popNode(); // top-level declaration
     popNode(); // Discard metadata
     pushNode(node);
     super.endTopLevelDeclaration(token);
   }
 
   @override
   void beginCompilationUnit(Token token) {
+    super.beginCompilationUnit(token);
     invalidTopLevelDeclarationCount = 0;
   }
 
   @override
   void endCompilationUnit(int count, Token token) {
     pushNode(makeNodeList(
         count - invalidTopLevelDeclarationCount, null, null, '\n'));
   }
 
   @override
@@ skipping 929 matching lines @@
     }
     lastErrorWasNativeFunctionBody = false;
   }
 
   void internalError({Token token, Node node}) {
     // TODO(ahe): This should call reporter.internalError.
     Spannable spannable = (token == null) ? node : token;
     failedAt(spannable, 'Internal error in parser.');
   }
 }