Revert "Making all callbacks use zones"

tools/dom/src/EventStreamProvider.dart

Index: tools/dom/src/EventStreamProvider.dart
diff --git a/tools/dom/src/EventStreamProvider.dart b/tools/dom/src/EventStreamProvider.dart
index eef7ebdfda582cf88fe96a68d64e4605569e366d..c794e0d0c9be6fe64509d76557f4624f259093f0 100644
--- a/tools/dom/src/EventStreamProvider.dart
+++ b/tools/dom/src/EventStreamProvider.dart
@@ -220,6 +220,12 @@ class _EventStreamSubscription<T extends Event> extends StreamSubscription<T> {
     _tryResume();
   }
 
+  static _wrapZone(callback) {
+    // For performance reasons avoid wrapping if we are in the root zone.
+    if (Zone.current == Zone.ROOT) return callback;
+    return Zone.current.bindUnaryCallback(callback, runGuarded: true);
+  }
+
   void cancel() {
     if (_canceled) return;