All strong mode cleaning of dart2js.

pkg/compiler/lib/src/js/rewrite_async.dart

 // 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
 // BSD-style license that can be found in the LICENSE file.
 
 library rewrite_async;
 
 import 'dart:collection';
 import 'dart:math' show max;
 
 import 'package:js_runtime/shared/async_await_error_codes.dart' as error_codes;
@@ skipping 2018 matching lines @@
   /// Also [nextWhenCanceled] is set up to contain the finally blocks that
   /// must be run in case the stream was canceled.
   @override
   void addYield(js.DartYield node, js.Expression expression) {
     // Find all the finally blocks that should be performed if the stream is
     // canceled during the yield.
     // At the bottom of the stack is the return label.
     List<int> enclosingFinallyLabels = <int>[exitLabel];
     enclosingFinallyLabels.addAll(jumpTargets
         .where((js.Node node) => finallyLabels[node] != null)
-        .map((js.Block node) => finallyLabels[node]));
+        .map((js.Node node) => finallyLabels[node]));
     addStatement(js.js.statement("# = #;", [
       nextWhenCanceled,
       new js.ArrayInitializer(enclosingFinallyLabels.map(js.number).toList())
     ]));
     addStatement(js.js.statement(
         """
         return #asyncStarHelper(#yieldExpression(#expression), #bodyName,
             #controller);""",
         {
           "asyncStarHelper": asyncStarHelper,
@@ skipping 564 matching lines @@
     return condition || body;
   }
 
   @override
   bool visitDartYield(js.DartYield node) {
     hasYield = true;
     visit(node.expression);
     return true;
   }
 }