Address late comments from CL 50313007.

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

Index: dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
diff --git a/dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart b/dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
index 9d9a89b3d2d6f10006559f594d83367db75f683e..74f447f811157a2a92e5602f637619fbcbd970ed 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
@@ -560,14 +560,14 @@ class ClassEmitter extends CodeEmitterHelper {
 
   void emitTypeVariableReaders(ClassElement cls, ClassBuilder builder) {
     List typeVariables = [];
-    ClassElement superclass = cls;
-    while (superclass != null) {
-      for (TypeVariableType parameter in superclass.typeVariables) {
+    ClassElement currentClass = cls;
+    while (currentClass != null) {
+      for (TypeVariableType parameter in currentClass.typeVariables) {
         if (task.readTypeVariables.contains(parameter.element)) {
           emitTypeVariableReader(cls, builder, parameter.element);
         }
       }
-      superclass = superclass.superclass;
+      currentClass = currentClass.superclass;
     }
   }