dart2js cleanup: remove unused imports and variables

pkg/compiler/lib/src/js_emitter/lazy_emitter/emitter.dart

 // Copyright (c) 2014, 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.js_emitter.lazy_emitter;
 
-import 'package:js_runtime/shared/embedded_names.dart'
-    show JsBuiltin, METADATA, TYPES;
+import 'package:js_runtime/shared/embedded_names.dart' show JsBuiltin;
 
 import '../../common.dart';
 import '../../compiler.dart' show Compiler;
 import '../../constants/values.dart' show ConstantValue;
 import '../../elements/elements.dart'
     show ClassElement, Element, FieldElement, FunctionElement;
 import '../../js/js.dart' as js;
 import '../../js_backend/js_backend.dart' show JavaScriptBackend, Namer;
-
 import '../js_emitter.dart' show NativeEmitter;
 import '../js_emitter.dart' as emitterTask show Emitter;
 import '../model.dart';
 import '../program_builder/program_builder.dart' show ProgramBuilder;
-
 import 'model_emitter.dart';
 
 class Emitter implements emitterTask.Emitter {
   final Compiler _compiler;
   final Namer namer;
   final ModelEmitter _emitter;
 
   JavaScriptBackend get _backend => _compiler.backend;
 
   Emitter(Compiler compiler, Namer namer, NativeEmitter nativeEmitter)
@@ skipping 144 matching lines @@
       default:
         reporter.internalError(
             NO_LOCATION_SPANNABLE, "Unhandled Builtin: $builtin");
         return null;
     }
   }
 
   @override
   void invalidateCaches() {}
 }