Fix inverted generic parameters.

lib/stream_channel.dart

Index: lib/stream_channel.dart
diff --git a/lib/stream_channel.dart b/lib/stream_channel.dart
index ff3104212f7077826b5c991530326288274528c7..7fff6744cd8c9b8b7e60d8c0a113f69887a4f41e 100644
--- a/lib/stream_channel.dart
+++ b/lib/stream_channel.dart
@@ -76,7 +76,7 @@ abstract class StreamChannel<T> {
   /// Transforms [this] using [transformer].
   ///
   /// This is identical to calling `transformer.bind(channel)`.
-  StreamChannel transform(StreamChannelTransformer<dynamic, T> transformer);
+  StreamChannel transform(StreamChannelTransformer<T, dynamic> transformer);
 
   /// Transforms only the [stream] component of [this] using [transformer].
   StreamChannel<T> transformStream(StreamTransformer<T, T> transformer);
@@ -113,7 +113,7 @@ abstract class StreamChannelMixin<T> implements StreamChannel<T> {
     other.stream.pipe(sink);
   }
 
-  StreamChannel transform(StreamChannelTransformer<dynamic, T> transformer) =>
+  StreamChannel transform(StreamChannelTransformer<T, dynamic> transformer) =>
       transformer.bind(this);
 
   StreamChannel<T> transformStream(StreamTransformer<T, T> transformer) =>