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

pkg/kernel/lib/binary/limited_ast_to_binary.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 'package:kernel/ast.dart';
 import 'package:kernel/binary/ast_to_binary.dart';
 
 /// Writes libraries that satisfy the [predicate].
 ///
 /// Only the referenced subset of canonical names is indexed and written,
@@ skipping 91 matching lines @@
   defaultMemberReference(Member node) {
     _handleReferencedName(node.canonicalName);
   }
 
   @override
   visitClassReference(Class node) {
     _handleReferencedName(node.canonicalName);
   }
 
   @override
-  visitLibrary(Library node) {
-    for (var reference in node.additionalExports) {
-      _handleReferencedName(reference.canonicalName);
-    }
-    super.visitLibrary(node);
-  }
-
-  @override
   visitLibraryDependency(LibraryDependency node) {
     _handleReferencedName(node.importedLibraryReference.canonicalName);
     super.visitLibraryDependency(node);
   }
 
   @override
   visitMethodInvocation(MethodInvocation node) {
     _handleReferencedName(node.interfaceTargetReference?.canonicalName);
     return super.visitMethodInvocation(node);
   }
@@ skipping 29 matching lines @@
   }
 
   void _handleReferencedName(CanonicalName name) {
     if (name == null || name.parent == null) return;
     _handleReferencedName(name.parent);
     referencedNames.add(name);
     name.index = -1;
     put(name.name);
   }
 }