Don't use "=>" for void methods in delegates.

lib/src/delegate/event_sink.dart

Index: lib/src/delegate/event_sink.dart
diff --git a/lib/src/delegate/event_sink.dart b/lib/src/delegate/event_sink.dart
index 1fe86c15ad23b68ef2246743c41b315b70d16dfc..337e7a811a9ddb3a2b277ffd61d8084d46d5ee69 100644
--- a/lib/src/delegate/event_sink.dart
+++ b/lib/src/delegate/event_sink.dart
@@ -16,10 +16,15 @@ class DelegatingEventSink<T> implements EventSink<T> {
   /// Create a delegating sink forwarding calls to [sink].
   DelegatingEventSink(EventSink sink) : _sink = sink;
 
-  void add(T data) => _sink.add(data);
+  void add(T data) {
+    _sink.add(data);
+  }
 
-  void addError(error, [StackTrace stackTrace]) =>
-      _sink.addError(error, stackTrace);
+  void addError(error, [StackTrace stackTrace]) {
+    _sink.addError(error, stackTrace);
+  }
 
-  void close() => _sink.close();
+  void close() {
+    _sink.close();
+  }
 }