package barback: Update the comment style generic syntax.

lib/src/transformer/aggregate_transform.dart

Index: lib/src/transformer/aggregate_transform.dart
diff --git a/lib/src/transformer/aggregate_transform.dart b/lib/src/transformer/aggregate_transform.dart
index a14a645aef01fbeab9107b74044bd2abc552218c..5c5fe6c8ebc7af8f6041f0a8d102e5f657f8abb2 100644
--- a/lib/src/transformer/aggregate_transform.dart
+++ b/lib/src/transformer/aggregate_transform.dart
@@ -81,7 +81,7 @@ class AggregateTransform extends BaseTransform {
   /// If an input with [id] cannot be found, throws an [AssetNotFoundException].
   Future<String> readInputAsString(AssetId id, {Encoding encoding}) {
     if (encoding == null) encoding = UTF8;
-    return getInput(id).then/*<Future<String>>*/(
+    return getInput(id).then<Future<String>>(
         (input) => input.readAsString(encoding: encoding));
   }