Avoid generating members for classes only for needed rti.

sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart

Index: sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart b/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
index 92e83fa9f0e60eba3aab846c51cc65ee601173b0..047cae4a7ad874313389d1ed6d2e735fe4133f51 100644
--- a/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
@@ -35,11 +35,15 @@ class ClassEmitter extends CodeEmitterHelper {
     }
 
     ClassBuilder builder = new ClassBuilder();
-    emitClassConstructor(classElement, builder, runtimeName);
+    if (!onlyForRti) {
+      emitClassConstructor(classElement, builder, runtimeName);
+    }
     emitFields(classElement, builder, superName, onlyForRti: onlyForRti);
-    emitClassGettersSetters(classElement, builder);
-    if (!classElement.isMixinApplication) {
-      emitInstanceMembers(classElement, builder);
+    if (!onlyForRti) {
+      emitClassGettersSetters(classElement, builder);
+      if (!classElement.isMixinApplication) {
+        emitInstanceMembers(classElement, builder);
+      }
     }
     task.typeTestEmitter.emitIsTests(classElement, builder);
 
@@ -226,7 +230,6 @@ class ClassEmitter extends CodeEmitterHelper {
 
   void emitClassGettersSetters(ClassElement classElement,
                                ClassBuilder builder) {
-
     visitFields(classElement, false,
                 (VariableElement member,
                  String name,