Use timeout to read most recent build from http

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';
@@ skipping 10 matching lines @@
   /// 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();
 
   @override
   Future<BuildResult> readResult(BuildUri buildUri) async {
-    try {
-      return await readBuildResultFromHttp(_client, buildUri);
-    } on HttpException {
-      return null;
-    } on SocketException {
-      return null;
+    Duration timeout;
+    if (buildUri.buildNumber < 0) {
+      timeout = new Duration(seconds: 1);
+    }
+
+    void skipToPreviousBuildNumber() {
+      BuildUri prevBuildUri = buildUri.prev();
+      log('Skip build number '
+          '${buildUri.buildNumber} -> ${prevBuildUri.buildNumber}');
+      buildUri = buildUri.prev();
+    }
+
+    while (true) {
+      try {
+        return await readBuildResultFromHttp(_client, buildUri, timeout);
+      } on TimeoutException {
+        if (timeout != null) {
+          skipToPreviousBuildNumber();
+          continue;
+        }
+        return null;
+      } on HttpException {
+        if (timeout != null) {
+          skipToPreviousBuildNumber();
+          continue;
+        }
+        return null;
+      } on SocketException {
+        return null;
+      }
     }
   }
 
-  int get mostRecentBuildNumber => -2;
+  int get mostRecentBuildNumber => -1;
 
   @override
   void close() {
     _client.close();
   }
 }
 
 /// Buildbot client that pulls build bot results through logdog.
 class LogdogBuildbotClient implements BuildbotClient {
   Map<String, List<int>> _botBuildNumberCache = <String, List<int>>{};
@@ skipping 38 matching lines @@
         buildUri = buildUri.withBuildNumber(buildNumber);
       }
     }
   }
 
   @override
   void close() {
     // Nothing to do.
   }
 }