Alternative fix for the js-interop crash.

pkg/compiler/lib/src/ssa/builder.dart

Index: pkg/compiler/lib/src/ssa/builder.dart
diff --git a/pkg/compiler/lib/src/ssa/builder.dart b/pkg/compiler/lib/src/ssa/builder.dart
index 0945568cfec8ca52f74c4eecf1ca669123a40266..c039418c4414e4e4024eecd624db28f8064ee038 100644
--- a/pkg/compiler/lib/src/ssa/builder.dart
+++ b/pkg/compiler/lib/src/ssa/builder.dart
@@ -5938,12 +5938,11 @@ class SsaBuilder extends ast.Visitor
       }
     }
 
+    DartType type = backend.helpers.jsJavaScriptObjectClass.thisType;
     var nativeBehavior = new native.NativeBehavior()
       ..codeTemplate = codeTemplate
-      ..typesReturned.add(
-          helpers.jsJavaScriptObjectClass.thisType)
-      ..typesInstantiated.add(
-          helpers.jsJavaScriptObjectClass.thisType)
+      ..typesReturned.add(type)
+      ..typesInstantiated.add(type)
       ..sideEffects.setAllSideEffects();
     return new HForeignCode(
         codeTemplate,