additional SDK fixes. This gets all of them, once we upgrade to new analyzer

tool/input_sdk/lib/async/stream.dart

 // Copyright (c) 2013, 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;
 
 // -------------------------------------------------------------------
 // Core Stream types
 // -------------------------------------------------------------------
 
@@ skipping 299 matching lines @@
    *
    * The returned stream is a broadcast stream if this stream is.
    */
   Stream asyncMap(convert(T event)) {
     StreamController controller;
     StreamSubscription subscription;
     void onListen () {
       final add = controller.add;
       assert(controller is _StreamController ||
              controller is _BroadcastStreamController);
-      final eventSink = controller;
+      final eventSink = controller as _EventSink<T>;
       final addError = eventSink._addError;
       subscription = this.listen(
           (T event) {
             var newValue;
             try {
               newValue = convert(event);
             } catch (e, s) {
               controller.addError(e, s);
               return;
             }
@@ skipping 39 matching lines @@
    * just as if it returned an empty stream.
    *
    * The returned stream is a broadcast stream if this stream is.
    */
   Stream asyncExpand(Stream convert(T event)) {
     StreamController controller;
     StreamSubscription subscription;
     void onListen() {
       assert(controller is _StreamController ||
              controller is _BroadcastStreamController);
-      final eventSink = controller;
+      final eventSink = controller as _EventSink<T>;
       subscription = this.listen(
           (T event) {
             Stream newStream;
             try {
               newStream = convert(event);
             } catch (e, s) {
               controller.addError(e, s);
               return;
             }
             if (newStream != null) {
@@ skipping 825 matching lines @@
 
     void onData(T event) {
       timer.cancel();
       controller.add(event);
       timer = zone.createTimer(timeLimit, timeout);
     }
     void onError(error, StackTrace stackTrace) {
       timer.cancel();
       assert(controller is _StreamController ||
              controller is _BroadcastStreamController);
-      var eventSink = controller;
+      var eventSink = controller as _EventSink<T>;
       eventSink._addError(error, stackTrace);  // Avoid Zone error replacement.
       timer = zone.createTimer(timeLimit, timeout);
     }
     void onDone() {
       timer.cancel();
       controller.close();
     }
     void onListen() {
       // This is the onListen callback for of controller.
       // It runs in the same zone that the subscription was created in.
@@ skipping 423 matching lines @@
 class _ControllerEventSinkWrapper<T> implements EventSink<T> {
   EventSink _sink;
   _ControllerEventSinkWrapper(this._sink);
 
   void add(T data) { _sink.add(data); }
   void addError(error, [StackTrace stackTrace]) {
     _sink.addError(error, stackTrace);
   }
   void close() { _sink.close(); }
 }