Revert "Store actual Reference(s) for additional exports."

pkg/kernel/lib/binary/ast_to_binary.dart

 // Copyright (c) 2016, 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 kernel.ast_to_binary;
 
 import '../ast.dart';
 import '../import_table.dart';
 import 'tag.dart';
 import 'dart:convert';
 import 'dart:typed_data';
@@ skipping 294 matching lines @@
   visitLibrary(Library node) {
     insideExternalLibrary = node.isExternal;
     node.binaryOffset = _sink.flushedLength + _sink.length;
     writeByte(insideExternalLibrary ? 1 : 0);
     writeCanonicalNameReference(getCanonicalNameOfLibrary(node));
     writeStringReference(node.name ?? '');
     // TODO(jensj): We save (almost) the same URI twice.
     writeUriReference(node.fileUri ?? '');
     writeAnnotationList(node.annotations);
     writeLibraryDependencies(node);
-    writeAdditionalExports(node);
     writeLibraryParts(node);
     writeNodeList(node.typedefs);
     writeNodeList(node.classes);
     writeNodeList(node.fields);
     writeNodeList(node.procedures);
   }
 
   void writeLibraryDependencies(Library library) {
     _libraryDependencyIndex = library.dependencies.isEmpty
         ? const <LibraryDependency, int>{}
         : <LibraryDependency, int>{};
     writeUInt30(library.dependencies.length);
     for (int i = 0; i < library.dependencies.length; ++i) {
       var importNode = library.dependencies[i];
       _libraryDependencyIndex[importNode] = i;
       writeLibraryDependency(importNode);
     }
   }
 
-  void writeAdditionalExports(Library library) {
-    writeUInt30(library.additionalExports.length);
-    for (Reference ref in library.additionalExports) {
-      writeReference(ref);
-    }
-  }
-
   void writeLibraryDependency(LibraryDependency node) {
     writeByte(node.flags);
     writeNodeList(node.annotations);
     writeLibraryReference(node.targetLibrary);
     writeStringReference(node.name ?? '');
     writeNodeList(node.combinators);
   }
 
   void visitCombinator(Combinator node) {
     writeByte(node.isShow ? 1 : 0);
@@ skipping 1209 matching lines @@
     _sink.add(_buffer.sublist(0, length));
     _buffer = new Uint8List(SIZE);
     flushedLength += length;
     length = 0;
   }
 
   void flushAndDestroy() {
     _sink.add(_buffer.sublist(0, length));
   }
 }