dart2js cleanup: remove unused imports and variables

pkg/compiler/lib/src/typechecker.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.typechecker;
 
-import 'common.dart';
 import 'common/names.dart' show Identifiers;
 import 'common/resolution.dart' show Resolution;
 import 'common/tasks.dart' show CompilerTask;
+import 'common.dart';
 import 'compiler.dart' show Compiler;
 import 'constants/expressions.dart';
 import 'constants/values.dart';
 import 'core_types.dart';
 import 'dart_types.dart';
 import 'elements/elements.dart'
     show
         AbstractFieldElement,
         AstElement,
         AsyncMarker,
         ClassElement,
         ConstructorElement,
         Element,
         Elements,
         EnumClassElement,
         EnumConstantElement,
         ExecutableElement,
         FieldElement,
         FunctionElement,
         GetterElement,
         InitializingFormalElement,
         LibraryElement,
-        Member,
         MemberSignature,
         Name,
         ParameterElement,
         PrivateName,
         PublicName,
         ResolvedAst,
         SetterElement,
         TypeDeclarationElement,
         TypedElement,
-        TypedefElement,
         VariableElement;
+import 'resolution/class_members.dart' show MembersCreator;
 import 'resolution/tree_elements.dart' show TreeElements;
-import 'resolution/class_members.dart' show MembersCreator;
 import 'tree/tree.dart';
 import 'util/util.dart' show Link, LinkBuilder;
 
 class TypeCheckerTask extends CompilerTask {
   TypeCheckerTask(Compiler compiler) : super(compiler);
   String get name => "Type checker";
 
   void check(AstElement element) {
     if (element.isClass) return;
     if (element.isTypedef) return;
@@ skipping 1955 matching lines @@
 
   visitTypedef(Typedef node) {
     // Do not typecheck [Typedef] nodes.
   }
 
   visitNode(Node node) {
     reporter.internalError(node,
         'Unexpected node ${node.getObjectDescription()} in the type checker.');
   }
 }