Fix buildbot_data_test

tools/gardening/lib/src/client.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 'dart:async';
 import 'dart:io' hide HttpException;
 
 import 'buildbot_data.dart';
 import 'buildbot_loading.dart';
 import 'buildbot_structures.dart';
 import 'logdog.dart';
 import 'util.dart';
 
 /// Interface for pulling build bot results.
 abstract class BuildbotClient {
   /// Reads the [BuildResult] for the [buildUri].
   Future<BuildResult> readResult(BuildUri buildUri);
 
   int get mostRecentBuildNumber;
 
   /// Closes the client and cleans up its state.
   void close();
 }
 
 /// Buildbot client that pulls build bot results through http.
 class HttpBuildbotClient implements BuildbotClient {
   final HttpClient _client = new HttpClient();
 
+  static const int maxSkips = 3;
+
   @override
   Future<BuildResult> readResult(BuildUri buildUri) async {
+    int skips = 0;
     Duration timeout;
     if (buildUri.buildNumber < 0) {
       timeout = new Duration(seconds: 1);
     }
 
     void skipToPreviousBuildNumber() {
       BuildUri prevBuildUri = buildUri.prev();
       log('Skip build number on ${buildUri} -> ${prevBuildUri.buildNumber}');
       buildUri = buildUri.prev();
     }
 
     while (true) {
       try {
         return await readBuildResultFromHttp(_client, buildUri, timeout);
       } on TimeoutException {
-        if (timeout != null) {
+        if (timeout != null && skips < maxSkips) {
+          skips++;
           skipToPreviousBuildNumber();
           continue;
         }
         return null;
       } on HttpException {
-        if (timeout != null) {
+        if (timeout != null && skips < maxSkips) {
+          skips++;
           skipToPreviousBuildNumber();
           continue;
         }
         return null;
       } on SocketException {
         return null;
       }
     }
   }
 
@@ skipping 49 matching lines @@
         buildUri = buildUri.withBuildNumber(buildNumber);
       }
     }
   }
 
   @override
   void close() {
     // Nothing to do.
   }
 }