Add BuildBotClient to abstract http/logdog access

tools/gardening/lib/src/buildbot_structures.dart

Index: tools/gardening/lib/src/buildbot_structures.dart
diff --git a/tools/gardening/lib/src/buildbot_structures.dart b/tools/gardening/lib/src/buildbot_structures.dart
index eee03a5290b06087c9f1aa946f189e684785d62e..3cbd500689e636ec6d8fe1607dede5edeffdda76 100644
--- a/tools/gardening/lib/src/buildbot_structures.dart
+++ b/tools/gardening/lib/src/buildbot_structures.dart
@@ -15,8 +15,8 @@ class BuildUri {
   final String suffix;
 
   factory BuildUri(Uri uri) {
-    List<String> parts =
-        split(uri.path, ['/builders/', '/builds/', '/steps/', '/logs/']);
+    List<String> parts = split(Uri.decodeFull(uri.path),
+        ['/builders/', '/builds/', '/steps/', '/logs/']);
     String botName = parts[1];
     int buildNumber = int.parse(parts[2]);
     String stepName = parts[3];
@@ -35,6 +35,8 @@ class BuildUri {
     return new BuildUri.fromData(botName, buildNumber, stepName);
   }
 
+  int get absoluteBuildNumber => buildNumber >= 0 ? buildNumber : null;
+
   String get shortBuildName => '$botName/$stepName';
 
   String get buildName =>