Remove dynamic parameters from Observatory helpers

runtime/observatory/lib/src/elements/helpers/rendering_scheduler.dart

Index: runtime/observatory/lib/src/elements/helpers/rendering_scheduler.dart
diff --git a/runtime/observatory/lib/src/elements/helpers/rendering_scheduler.dart b/runtime/observatory/lib/src/elements/helpers/rendering_scheduler.dart
index e3e81e07c22b06d3b4f8ff2af07fc9624ffbd9fd..a04903ef7d57ccee352772651eefef5cb1fd9bdd 100644
--- a/runtime/observatory/lib/src/elements/helpers/rendering_scheduler.dart
+++ b/runtime/observatory/lib/src/elements/helpers/rendering_scheduler.dart
@@ -91,7 +91,7 @@ class RenderingScheduler<T extends Renderable> implements RenderingTask {
   /// Checks for modification during attribute set.
   /// If value changes a new rendering is scheduled.
   /// set attr(T v) => _attr = _r.checkAndReact(_attr, v);
-  dynamic checkAndReact(dynamic oldValue, dynamic newValue) {
+  T checkAndReact<T>(T oldValue, T newValue) {
     if (oldValue != newValue)
       dirty();
     else