Fixed bug: last entry was missing from shard_data.dart

tools/gardening/bin/create_shard_groups.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.
 
 // Outputs source code for `part` used by `shard2group.dart`. Usage:
 // `dart bin/create_shard_groups.dart source.html >lib/src/shard_data.dart`.
 
 import 'dart:io';
 import 'dart:math' as math;
 
@@ skipping 23 matching lines @@
 const String shardMark = '/builders/';
 
 List<List<String>> findShards(List<String> source) {
   List<List<String>> result = <List<String>>[];
   List<String> shardResult;
   bool started = false;
 
   for (String line in source) {
     if (line.contains(shardsStartMark)) started = true;
     if (started) {
-      if (line.contains(shardsEndMark)) break;
+      if (line.contains(shardsEndMark)) {
+        if (shardResult != null) result.add(shardResult);
+        break;
+      }
       String trimmed = line.trim();
       int buildersIndex = trimmed.indexOf(shardMark);
       if (buildersIndex >= 0) {
         int quoteIndex = trimmed.indexOf("'", buildersIndex);
         if (quoteIndex >= 0) {
           // Found a shard name, add it.
           shardResult.add(trimmed.substring(
               buildersIndex + shardMark.length, quoteIndex));
         } else {
           // Unexpected source formatting, skip.
@@ skipping 35 matching lines @@
 """);
   for (int i = 0; i < groupCount; i++) {
     print("  '${groups[i]}': const <String>[");
     for (List<String> shard in shards[i]) {
       print("    '$shard',");
     }
     print("  ],");
   }
   print('};');
 }