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

runtime/vm/kernel_binary_flowgraph.h

 // 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.
 
 #ifndef RUNTIME_VM_KERNEL_BINARY_FLOWGRAPH_H_
 #define RUNTIME_VM_KERNEL_BINARY_FLOWGRAPH_H_
 
 #if !defined(DART_PRECOMPILED_RUNTIME)
 
 #include <map>
@@ skipping 384 matching lines @@
 // If asked to read a compound field (e.g. an expression) it will be skipped.
 class LibraryHelper {
  public:
   enum Field {
     kFlags,
     kCanonicalName,
     kName,
     kSourceUriIndex,
     kAnnotations,
     kDependencies,
-    kAdditionalExports,
     kParts,
     kTypedefs,
     kClasses,
     kToplevelField,
     kToplevelProcedures,
     kEnd,
   };
 
   enum Flag {
     kExternal = 1,
@@ skipping 716 matching lines @@
   const uint8_t* saved_raw_buffer_;
   const TypedData* saved_typed_data_;
   intptr_t saved_offset_;
 };
 
 }  // namespace kernel
 }  // namespace dart
 
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)
 #endif  // RUNTIME_VM_KERNEL_BINARY_FLOWGRAPH_H_