dart2js: Remove unused variable.

pkg/compiler/lib/src/js_emitter/old_emitter/container_builder.dart

Index: pkg/compiler/lib/src/js_emitter/old_emitter/container_builder.dart
diff --git a/pkg/compiler/lib/src/js_emitter/old_emitter/container_builder.dart b/pkg/compiler/lib/src/js_emitter/old_emitter/container_builder.dart
index 981ed489d31d8285a91eb1fc3f0aca80020f45d2..b882d6dfbd568df659970175f9b62dacc713ce5a 100644
--- a/pkg/compiler/lib/src/js_emitter/old_emitter/container_builder.dart
+++ b/pkg/compiler/lib/src/js_emitter/old_emitter/container_builder.dart
@@ -9,8 +9,6 @@ part of dart2js.js_emitter;
 /// Initially, it is just a placeholder for code that is moved from
 /// [CodeEmitterTask].
 class ContainerBuilder extends CodeEmitterHelper {
-  final Map<Element, Element> staticGetters = new Map<Element, Element>();
-
   bool needsSuperGetter(FunctionElement element) =>
     compiler.codegenWorld.methodsNeedingSuperGetter.contains(element);