Migrate the samples to one-argument version of requestAnimationFrame and re-enable the test.

samples/ui_lib/base/AnimationScheduler.dart

Index: samples/ui_lib/base/AnimationScheduler.dart
diff --git a/samples/ui_lib/base/AnimationScheduler.dart b/samples/ui_lib/base/AnimationScheduler.dart
index 73d7381ae1b0c5ba428e45034e76478ab0539cd2..80b15288bb6b2d1fa616d597f57d98697bcd787c 100644
--- a/samples/ui_lib/base/AnimationScheduler.dart
+++ b/samples/ui_lib/base/AnimationScheduler.dart
@@ -97,7 +97,7 @@ class AnimationScheduler {
         try {
           // TODO(jacobr): passing in document should not be required.
           _intervalId = window.webkitRequestAnimationFrame(
-              (int ignored) { _step(); }, document);
+              (int ignored) { _step(); });
               // TODO(jacobr) fix this odd type error.
         } catch (var e) {
           _webkitAnimationFrameMaybeAvailable = false;