Add typed wrapper functions to delegate classes.

lib/src/lazy_stream.dart

Index: lib/src/lazy_stream.dart
diff --git a/lib/src/lazy_stream.dart b/lib/src/lazy_stream.dart
index 3ba49531fcf555369a5f28f33b085946d1b8e448..147fa8bd5f2984b66335bc4a78f8b9b8e2648a3b 100644
--- a/lib/src/lazy_stream.dart
+++ b/lib/src/lazy_stream.dart
@@ -5,6 +5,7 @@
 import "dart:async";
 
 import "stream_completer.dart";
+import "delegate/stream.dart";
 
 /// A [Stream] wrapper that forwards to another [Stream] that's initialized
 /// lazily.
@@ -39,9 +40,14 @@ class LazyStream<T> extends Stream<T> {
     _callback = null;
     var result = callback();
 
-    Stream stream = result is Future
-        ? StreamCompleter.fromFuture(result)
-        : result;
+    Stream<T> stream;
+    if (result is Future) {
+      stream = StreamCompleter.fromFuture(result.then((stream) {
+        return DelegatingStream.typed/*<T>*/(stream as Stream);
+      }));
+    } else {
+      stream = DelegatingStream.typed/*<T>*/(result as Stream);
+    }
 
     return stream.listen(onData,
         onError: onError, onDone: onDone, cancelOnError: cancelOnError);