Make Zone API strong mode clean.

sdk/lib/async/stream_impl.dart

 // 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
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart.async;
 
 /** Abstract and private interface for a place to put events. */
 abstract class _EventSink<T> {
   void _add(T data);
   void _addError(Object error, StackTrace stackTrace);
@@ skipping 314 matching lines @@
     assert(!_isCanceled);
     assert(!_isPaused);
     assert(!_inCallback);
     bool wasInputPaused = _isInputPaused;
     _state |= _STATE_IN_CALLBACK;
     _zone.runUnaryGuarded(_onData, data);
     _state &= ~_STATE_IN_CALLBACK;
     _checkState(wasInputPaused);
   }
 
-  void _sendError(var error, StackTrace stackTrace) {
+  void _sendError(Object error, StackTrace stackTrace) {
     assert(!_isCanceled);
     assert(!_isPaused);
     assert(!_inCallback);
     bool wasInputPaused = _isInputPaused;
 
     void sendError() {
       // If the subscription has been canceled while waiting for the cancel
       // future to finish we must not report the error.
       if (_isCanceled && !_waitsForCancel) return;
       _state |= _STATE_IN_CALLBACK;
       // TODO(floitsch): this dynamic should be 'void'.
       if (_onError is ZoneBinaryCallback<dynamic, Object, StackTrace>) {
-        ZoneBinaryCallback<dynamic, Object, StackTrace> errorCallback = _onError
-            as Object/*=ZoneBinaryCallback<dynamic, Object, StackTrace>*/;
+        ZoneBinaryCallback<dynamic, Object, StackTrace> errorCallback =
+            _onError;
         _zone.runBinaryGuarded(errorCallback, error, stackTrace);
       } else {
-        _zone.runUnaryGuarded<dynamic, Object>(
-            _onError as Object/*=ZoneUnaryCallback<dynamic, Object>*/, error);
+        _zone.runUnaryGuarded<Object>(_onError, error);
       }
       _state &= ~_STATE_IN_CALLBACK;
     }
 
     if (_cancelOnError) {
       _state |= _STATE_WAIT_FOR_CANCEL;
       _cancel();
       if (_cancelFuture is Future &&
           !identical(_cancelFuture, Future._nullFuture)) {
         _cancelFuture.whenComplete(sendError);
@@ skipping 678 matching lines @@
 
 /** An empty broadcast stream, sending a done event as soon as possible. */
 class _EmptyStream<T> extends Stream<T> {
   const _EmptyStream() : super._internal();
   bool get isBroadcast => true;
   StreamSubscription<T> listen(void onData(T data),
       {Function onError, void onDone(), bool cancelOnError}) {
     return new _DoneStreamSubscription<T>(onDone);
   }
 }