Put "super" in quotes.

dart/lib/compiler/implementation/js_backend/emitter.dart

Index: dart/lib/compiler/implementation/js_backend/emitter.dart
diff --git a/dart/lib/compiler/implementation/js_backend/emitter.dart b/dart/lib/compiler/implementation/js_backend/emitter.dart
index eaf1f1a78bff1c7232a3aa4d7ef91bccaa950fdb..9b56b192485c3a7d6398eacb47f81da6b692b766 100644
--- a/dart/lib/compiler/implementation/js_backend/emitter.dart
+++ b/dart/lib/compiler/implementation/js_backend/emitter.dart
@@ -567,7 +567,7 @@ function(collectedClasses) {
     // TODO(floitsch): the emitInstanceMember should simply always emit a ',\n'.
     // That does currently not work because the native classes have a different
     // syntax.
-    buffer.add(' super: "$superName"');
+    buffer.add(' "super": "$superName"');
     emitInstanceMembers(classElement, buffer, true);
     buffer.add('\n};\n\n');
   }