dart2js cleanup: remove unused imports and variables

pkg/compiler/lib/src/resolution/resolution.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.resolution;
 
 import 'dart:collection' show Queue;
 
 import '../common.dart';
 import '../common/names.dart' show Identifiers;
 import '../common/resolution.dart'
     show Feature, Parsing, Resolution, ResolutionImpact;
-import '../common/tasks.dart' show CompilerTask, DeferredAction;
+import '../common/tasks.dart' show CompilerTask;
+import '../compile_time_constants.dart' show ConstantCompiler;
 import '../compiler.dart' show Compiler;
-import '../compile_time_constants.dart' show ConstantCompiler;
 import '../constants/expressions.dart'
     show
         ConstantExpression,
         ConstantExpressionKind,
         ConstructedConstantExpression,
         ErroneousConstantExpression;
 import '../constants/values.dart' show ConstantValue;
 import '../core_types.dart' show CoreClasses, CoreTypes;
 import '../dart_types.dart';
 import '../elements/elements.dart';
@@ skipping 14 matching lines @@
     show
         isBinaryOperator,
         isMinusOperator,
         isTernaryOperator,
         isUnaryOperator,
         isUserDefinableOperator;
 import '../tree/tree.dart';
 import '../universe/call_structure.dart' show CallStructure;
 import '../universe/use.dart' show StaticUse, TypeUse;
 import '../universe/world_impact.dart' show WorldImpact;
-import '../util/util.dart' show Link, LinkBuilder, Setlet;
-
+import '../util/util.dart' show Link, Setlet;
 import 'class_hierarchy.dart';
 import 'class_members.dart' show MembersCreator;
 import 'constructors.dart';
 import 'members.dart';
 import 'registry.dart';
 import 'signatures.dart';
 import 'tree_elements.dart';
 import 'typedefs.dart';
 
 class ResolverTask extends CompilerTask {
@@ skipping 1029 matching lines @@
   TreeElements get treeElements {
     assert(invariant(this, _treeElements != null,
         message: "TreeElements have not been computed for $this."));
     return _treeElements;
   }
 
   void reuseElement() {
     _treeElements = null;
   }
 }