dart2js cleanup: remove unused imports and variables

pkg/compiler/lib/src/mirrors/dart2js_mirrors.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.mirrors;
 
 import 'dart:collection' show UnmodifiableListView, UnmodifiableMapView;
 
 import '../common.dart';
 import '../compiler.dart' show Compiler;
 import '../constants/expressions.dart';
 import '../constants/values.dart';
 import '../dart_types.dart';
 import '../elements/elements.dart';
 import '../elements/modelx.dart' show LibraryElementX;
 import '../resolution/scope.dart' show Scope;
 import '../script.dart';
 import '../tokens/token.dart';
 import '../tokens/token_constants.dart' as Tokens;
 import '../tree/tree.dart';
-import '../util/util.dart' show Link, LinkBuilder;
 import '../util/characters.dart' show $CR, $LF;
+import '../util/util.dart' show Link;
+import 'mirrors_util.dart';
+import 'source_mirrors.dart';
 
-import 'source_mirrors.dart';
-import 'mirrors_util.dart';
-
+part 'dart2js_instance_mirrors.dart';
 part 'dart2js_library_mirror.dart';
+part 'dart2js_member_mirrors.dart';
 part 'dart2js_type_mirrors.dart';
-part 'dart2js_member_mirrors.dart';
-part 'dart2js_instance_mirrors.dart';
 
 //------------------------------------------------------------------------------
 // Utility types and functions for the dart2js mirror system
 //------------------------------------------------------------------------------
 
 bool _includeLibrary(Dart2JsLibraryMirror mirror) {
   return const bool.fromEnvironment("list_all_libraries") ||
       !mirror._element.isInternalLibrary;
 }
 
@@ skipping 431 matching lines @@
     if (!parameter.hasDefaultValue) return null;
     ParameterElement parameterElement = parameter._element;
     Compiler compiler = parameter.mirrorSystem.compiler;
     return compiler.constants.getConstantForVariable(parameterElement);
   }
 
   static Mirror getMirrorFromElement(Dart2JsMirror mirror, Element element) {
     return _convertElementToDeclarationMirror(mirror.mirrorSystem, element);
   }
 }