Run DOM callbacks in the zone they are coming from.

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 a9c293da5da7083b938ffbd80785bdea4cf32068..5d6c0daac11dca4a919236215a02e987e8dc911b 100644
--- a/tools/dom/src/EventStreamProvider.dart
+++ b/tools/dom/src/EventStreamProvider.dart
@@ -154,11 +154,17 @@ class _EventStreamSubscription<T extends Event> extends StreamSubscription<T> {
   var _onData;
   final bool _useCapture;
 
-  _EventStreamSubscription(this._target, this._eventType, this._onData,
-      this._useCapture) {
+  _EventStreamSubscription(this._target, this._eventType, onData,
+      this._useCapture) : _onData = _wrapZone(onData) {
     _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);
+  }
+
   void cancel() {
     if (_canceled) return;
 
@@ -177,7 +183,7 @@ class _EventStreamSubscription<T extends Event> extends StreamSubscription<T> {
     // Remove current event listener.
     _unlisten();
 
-    _onData = handleData;
+    _onData = _wrapZone(handleData);
     _tryResume();
   }