Add find_timeouts and caching to tools/gardening

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;
 
 const String groupsStartMark = r"<td class='DevStatus Alt first";
 const String groupsEndMark = r"<tr class='DevStatusSpacing'>";
 
 List<String> findGroups(List<String> source) {
   List<String> result = <String>[];
   bool started = false;
-  
+
   for (String line in source) {
     if (line.contains(groupsStartMark)) started = true;
     if (started) {
       if (line.contains(groupsEndMark)) break;
       String trimmed = line.trim();
       if (!trimmed.startsWith('<')) {
         result.add(trimmed);
       }
     }
   }
@@ skipping 16 matching lines @@
       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));
+          shardResult.add(
+              trimmed.substring(buildersIndex + shardMark.length, quoteIndex));
         } else {
           // Unexpected source formatting, skip.
         }
       } else if (trimmed.contains(shardsGroupStartMark)) {
         // This is a group separator, switch to next sublist.
         if (shardResult != null) result.add(shardResult);
         shardResult = <String>[];
       }
     }
   }
-  return result;  
+  return result;
 }
 
 main(List<String> args) {
   if (args.length != 1) {
     print('Usage: dart create_shard_groups.dart <darto-source-file>');
     exit(1);
   }
 
   File dartoSourceFile = new File(args[0]);
   List<String> dartoSource = dartoSourceFile.readAsLinesSync();
@@ skipping 16 matching lines @@
 """);
   for (int i = 0; i < groupCount; i++) {
     print("  '${groups[i]}': const <String>[");
     for (String shard in shards[i]) {
       print("    '$shard',");
     }
     print("  ],");
   }
   print('};');
 }