Add stack chain support to pub.

sdk/lib/_internal/pub/lib/src/command/uploader.dart

Index: sdk/lib/_internal/pub/lib/src/command/uploader.dart
diff --git a/sdk/lib/_internal/pub/lib/src/command/uploader.dart b/sdk/lib/_internal/pub/lib/src/command/uploader.dart
index 330efcc0e31df04c7085717c631ddae5e0b25860..515866215673389d48d97d678e93e4bc42f1eb03 100644
--- a/sdk/lib/_internal/pub/lib/src/command/uploader.dart
+++ b/sdk/lib/_internal/pub/lib/src/command/uploader.dart
@@ -16,6 +16,7 @@ import '../io.dart';
 import '../log.dart' as log;
 import '../oauth2.dart' as oauth2;
 import '../source/hosted.dart';
+import '../utils.dart';
 
 /// Handles the `uploader` pub command.
 class UploaderCommand extends PubCommand {
@@ -57,7 +58,7 @@ class UploaderCommand extends PubCommand {
       return flushThenExit(exit_codes.USAGE);
     }
 
-    return new Future.sync(() {
+    return syncFuture(() {
       var package = commandOptions['package'];
       if (package != null) return package;
       return new Entrypoint(path.current, cache).root.name;