Small improvements to bot summary.

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 12 matching lines @@
 }
 
 /// 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 {
+    } on HttpException catch (e) {
+      return null;
+    } on SocketException catch (e) {
       return null;
     }
   }
 
   int get mostRecentBuildNumber => -2;
 
   @override
   void close() {
     _client.close();
   }
@@ skipping 43 matching lines @@
         buildUri = buildUri.withBuildNumber(buildNumber);
       }
     }
   }
 
   @override
   void close() {
     // Nothing to do.
   }
 }