dart2js: fix method setup on mixin classes in the new emitter.

pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart

Index: pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart b/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
index 30d81ed1bd78fa86541919b585709b48c649539f..238f88a7eab1ef8481bc9bd60198a5e00803b9d2 100644
--- a/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
@@ -785,7 +785,7 @@ function parseFunctionDescriptor(proto, name, descriptor) {
     if (typeof descriptor[2] !== 'function') {
       constructor = compileMixinConstructor(name, prototype, descriptor);
       for (var i = 4; i < descriptor.length; i += 2) {
-        parseFunctionDescriptor(prototype, descriptor, descriptor[i + 1]);
+        parseFunctionDescriptor(prototype, descriptor[i], descriptor[i + 1]);
       }
     } else {
       constructor = descriptor[2];