dart2js cleanup: remove unused imports and variables

pkg/compiler/lib/src/common/registry.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.common.registry;
 
 import '../dart_types.dart' show InterfaceType;
+import '../elements/elements.dart' show Element;
 import '../enqueue.dart' show Enqueuer;
-import '../elements/elements.dart' show Element, FunctionElement;
 import '../universe/use.dart' show DynamicUse, StaticUse;
 
 /// Interface for registration of element dependencies.
 abstract class Registry {
   // TODO(johnniwinther): Remove this.
   void registerDependency(Element element) {}
 
   bool get isForResolution;
 
   void registerDynamicUse(DynamicUse staticUse);
@@ skipping 22 matching lines @@
     world.registerInstantiatedType(type);
   }
 
   @override
   void registerStaticUse(StaticUse staticUse) {
     world.registerStaticUse(staticUse);
   }
 
   String toString() => name;
 }