TBR. Add back fix to the misleading types for onError. Otherwise, html/worker_test/functional fails…

sdk/lib/html/dart2js/html_dart2js.dart

Index: sdk/lib/html/dart2js/html_dart2js.dart
diff --git a/sdk/lib/html/dart2js/html_dart2js.dart b/sdk/lib/html/dart2js/html_dart2js.dart
index 3d48d6087af93ccc3e7e503cdef3075aec596fc8..accb6fe7ad762d81247471a8c1818c49ae90d850 100644
--- a/sdk/lib/html/dart2js/html_dart2js.dart
+++ b/sdk/lib/html/dart2js/html_dart2js.dart
@@ -143,12 +143,12 @@ abstract class AbstractWorker extends Interceptor implements EventTarget {
    */
   @DomName('AbstractWorker.errorEvent')
   @DocsEditable()
-  static const EventStreamProvider<ErrorEvent> errorEvent = const EventStreamProvider<ErrorEvent>('error');
+  static const EventStreamProvider<Event> errorEvent = const EventStreamProvider<Event>('error');
 
   /// Stream of `error` events handled by this [AbstractWorker].
   @DomName('AbstractWorker.onerror')
   @DocsEditable()
-  Stream<ErrorEvent> get onError => errorEvent.forTarget(this);
+  Stream<Event> get onError => errorEvent.forTarget(this);
 }
 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
@@ -3201,7 +3201,7 @@ class CompositorWorker extends EventTarget implements AbstractWorker {
   @DomName('CompositorWorker.errorEvent')
   @DocsEditable()
   @Experimental() // untriaged
-  static const EventStreamProvider<ErrorEvent> errorEvent = const EventStreamProvider<ErrorEvent>('error');
+  static const EventStreamProvider<Event> errorEvent = const EventStreamProvider<Event>('error');
 
   @DomName('CompositorWorker.messageEvent')
   @DocsEditable()
@@ -3247,7 +3247,7 @@ class CompositorWorker extends EventTarget implements AbstractWorker {
   @DomName('CompositorWorker.onerror')
   @DocsEditable()
   @Experimental() // untriaged
-  Stream<ErrorEvent> get onError => errorEvent.forTarget(this);
+  Stream<Event> get onError => errorEvent.forTarget(this);
 
   @DomName('CompositorWorker.onmessage')
   @DocsEditable()
@@ -30052,7 +30052,7 @@ class SharedWorker extends EventTarget implements AbstractWorker {
   @DomName('SharedWorker.errorEvent')
   @DocsEditable()
   @Experimental() // untriaged
-  static const EventStreamProvider<ErrorEvent> errorEvent = const EventStreamProvider<ErrorEvent>('error');
+  static const EventStreamProvider<Event> errorEvent = const EventStreamProvider<Event>('error');
 
   @DomName('SharedWorker.SharedWorker')
   @DocsEditable()
@@ -30077,7 +30077,7 @@ class SharedWorker extends EventTarget implements AbstractWorker {
   @DomName('SharedWorker.onerror')
   @DocsEditable()
   @Experimental() // untriaged
-  Stream<ErrorEvent> get onError => errorEvent.forTarget(this);
+  Stream<Event> get onError => errorEvent.forTarget(this);
 }
 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
@@ -36750,7 +36750,7 @@ class Worker extends EventTarget implements AbstractWorker {
   @DomName('Worker.errorEvent')
   @DocsEditable()
   @Experimental() // untriaged
-  static const EventStreamProvider<ErrorEvent> errorEvent = const EventStreamProvider<ErrorEvent>('error');
+  static const EventStreamProvider<Event> errorEvent = const EventStreamProvider<Event>('error');
 
   /**
    * Static factory designed to expose `message` events to event
@@ -36801,7 +36801,7 @@ class Worker extends EventTarget implements AbstractWorker {
   @DomName('Worker.onerror')
   @DocsEditable()
   @Experimental() // untriaged
-  Stream<ErrorEvent> get onError => errorEvent.forTarget(this);
+  Stream<Event> get onError => errorEvent.forTarget(this);
 
   /// Stream of `message` events handled by this [Worker].
   @DomName('Worker.onmessage')