In summary/stats.dart, don't count enums with index == 0.

pkg/analyzer/tool/summary/stats.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.
 
 /**
  * This file contains code for collecting statistics about the use of fields in
  * a summary file.
  */
 library analyzer.tool.summary.stats;
 
 import 'dart:io';
+import 'dart:mirrors';
 
 import 'package:analyzer/src/summary/base.dart';
 import 'package:analyzer/src/summary/idl.dart';
 
 main(List<String> args) {
   if (args.length != 1) {
     _printUsage();
     exitCode = 1;
     return;
   }
@@ skipping 51 matching lines @@
    * Record statistics for [obj] and all objects it refers to.
    */
   void record(SummaryClass obj) {
     Map<String, int> typeCounts =
         counts.putIfAbsent(obj.runtimeType, () => <String, int>{});
     obj.toMap().forEach((String key, Object value) {
       if (value == null ||
           value == 0 ||
           value == false ||
           value == '' ||
-          value is List && value.isEmpty) {
+          value is List && value.isEmpty ||
+          reflect(value).type.isEnum && (value as dynamic).index == 0) {
         return;
       }
       if (!typeCounts.containsKey(key)) {
         typeCounts[key] = 0;
       }
       typeCounts[key]++;
       if (value is SummaryClass) {
         record(value);
       } else if (value is List) {
         value.forEach((Object element) {
           if (element is SummaryClass) {
             record(element);
           }
         });
       }
     });
   }
 }