Allow a wider pub constraint on barback.

sdk/lib/_internal/pub/test/implicit_barback_dependency_test.dart

Index: sdk/lib/_internal/pub/test/implicit_barback_dependency_test.dart
diff --git a/sdk/lib/_internal/pub/test/implicit_barback_dependency_test.dart b/sdk/lib/_internal/pub/test/implicit_barback_dependency_test.dart
index 894cf5163c9bf3772899983bf86b09828676932c..3bc488a6ab454975eae28abef3df4c8314ddb38f 100644
--- a/sdk/lib/_internal/pub/test/implicit_barback_dependency_test.dart
+++ b/sdk/lib/_internal/pub/test/implicit_barback_dependency_test.dart
@@ -10,11 +10,11 @@ import '../lib/src/version.dart';
 main() {
   initConfig();
 
-  var current = barback.supportedVersion.toString();
-  var previous = new Version(barback.supportedVersion.major,
-      barback.supportedVersion.minor - 1, 0).toString();
-  var nextPatch = barback.supportedVersion.nextPatch.toString();
-  var max = barback.supportedVersion.nextMinor.toString();
+  var current = barback.supportedVersions.min.toString();
+  var previous = new Version(barback.supportedVersions.min.major,
+      barback.supportedVersions.min.minor - 1, 0).toString();
+  var nextPatch = barback.supportedVersions.min.nextPatch.toString();
+  var max = barback.supportedVersions.max.toString();
 
   forBothPubGetAndUpgrade((command) {
     integration("implicitly constrains barback to versions pub supports", () {
@@ -32,7 +32,7 @@ main() {
       pubCommand(command);
 
       d.packagesDir({
-        "barback": barback.supportedVersion.nextPatch.toString()
+        "barback": barback.supportedVersions.min.nextPatch.toString()
       }).validate();
     });