Use timeout to read most recent build from http

tools/gardening/lib/src/buildbot_loading.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';
 import 'util.dart';
 
 import 'buildbot_structures.dart';
 import 'cache.dart';
@@ skipping 15 matching lines @@
     }
     return result;
   } else {
     return parseTestStepResult(
         buildUri, await cache.read(buildUri.logdogPath, read));
   }
 }
 
 /// Fetches test data for [buildUri] through the buildbot stdio.
 Future<BuildResult> readBuildResultFromHttp(
-    HttpClient client, BuildUri buildUri) {
+    HttpClient client, BuildUri buildUri,
+    [Duration timeout]) {
   Future<String> read() async {
     Uri uri = buildUri.toUri();
     log('Reading buildbot results: $uri');
-    return readUriAsText(client, uri);
+    return readUriAsText(client, uri, timeout);
   }
 
   return _readBuildResult(buildUri, read);
 }
 
 /// Fetches test data for [buildUri] through logdog.
 ///
 /// The build number of [buildUri] most be non-negative.
 Future<BuildResult> readBuildResultFromLogDog(BuildUri buildUri) {
   Future<String> read() async {
@@ skipping 87 matching lines @@
     String archName = name.substring(0, slashPos);
     String testName = name.substring(slashPos + 1);
     timings.add(new Timing(
         uri,
         time,
         new TestStep(
             stepName, new TestConfiguration(configName, archName, testName))));
   }
   return timings;
 }