The execution of an async* should only be scheduled when the stream is

pkg/compiler/lib/src/ssa/builder.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 ssa;
 
 class SsaFunctionCompiler implements FunctionCompiler {
   SsaCodeGeneratorTask generator;
   SsaBuilderTask builder;
   SsaOptimizerTask optimizer;
@@ skipping 34 matching lines @@
             yieldStarExpression: backend.emitter.staticFunctionAccess(
                 backend.getYieldStar()),
             safeVariableName: backend.namer.safeVariableName);
       }
       else if (element.asyncMarker == AsyncMarker.ASYNC_STAR) {
         rewriter = new AsyncRewriter(
             backend.compiler,
             backend.compiler.currentElement,
             streamHelper: backend.emitter.staticFunctionAccess(
                 backend.getStreamHelper()),
+            streamOfController: backend.emitter.staticFunctionAccess(
+                backend.getStreamOfController()),
             newController: backend.emitter.staticFunctionAccess(
                 backend.getASyncStarControllerConstructor()),
             safeVariableName: backend.namer.safeVariableName,
             yieldExpression: backend.emitter.staticFunctionAccess(
                 backend.getYieldSingle()),
             yieldStarExpression: backend.emitter.staticFunctionAccess(
                 backend.getYieldStar()));
       }
       if (rewriter != null) {
         result = rewriter.rewrite(result);
@@ skipping 6819 matching lines @@
     if (unaliased is TypedefType) throw 'unable to unalias $type';
     unaliased.accept(this, builder);
   }
 
   void visitDynamicType(DynamicType type, SsaBuilder builder) {
     JavaScriptBackend backend = builder.compiler.backend;
     ClassElement cls = backend.findHelper('DynamicRuntimeType');
     builder.push(new HDynamicType(type, new TypeMask.exact(cls, classWorld)));
   }
 }