- Parse the return type of JS during resolution to know what can be instantiated there.

sdk/lib/_internal/compiler/implementation/enqueue.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 dart2js;
 
 class EnqueueTask extends CompilerTask {
   final Enqueuer codegen;
   final Enqueuer resolution;
 
@@ skipping 374 matching lines @@
       registerNewSelector(setterName,
                           new TypedSelector(type, setter),
                           universe.fieldSetters);
     });
   }
 
   void registerIsCheck(DartType type) {
     universe.isChecks.add(type);
   }
 
+  void registerJsCall(Send node, ResolverVisitor resolver) {
+    nativeEnqueuer.registerJsCall(node, this, resolver);
+  }
+  
+
   void forEach(f(WorkItem work)) {
     while (!queue.isEmpty) {
       f(queue.removeLast()); // TODO(kasperl): Why isn't this removeFirst?
     }
   }
 
   String toString() => 'Enqueuer($name)';
 
   void logSummary(log(message)) {
     log(isResolutionQueue
         ? 'Resolved ${resolvedElements.length} elements.'
         : 'Compiled ${universe.generatedCode.length} methods.');
     nativeEnqueuer.logSummary(log);
   }
 }