Add BuildBotClient to abstract http/logdog access

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 95 matching lines @@
     if (line.startsWith('--- Total time:')) {
       parsingTimingBlock = true;
     } else if (parsingTimingBlock) {
       if (line.startsWith('0:')) {
         timings.addAll(parseTimings(buildUri, line));
       } else {
         parsingTimingBlock = false;
       }
     }
   }
-  return new BuildResult(buildUri, buildNumber, results, failures, timings);
+  return new BuildResult(buildUri, buildNumber ?? buildUri.absoluteBuildNumber,
+      results, failures, timings);
 }
 
 /// Create the [Timing]s for the [line] as found in the top-20 timings of a
 /// build step stdio log.
 List<Timing> parseTimings(BuildUri uri, String line) {
   List<String> parts = split(line, [' - ', ' - ', ' ']);
   String time = parts[0];
   String stepName = parts[1];
   String configName = parts[2];
   String testNames = parts[3];
   List<Timing> timings = <Timing>[];
   for (String name in testNames.split(',')) {
     name = name.trim();
     int slashPos = name.indexOf('/');
     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;
 }