dart2js cleanup: remove unused imports and variables

pkg/compiler/lib/src/mirrors_used.dart

 // Copyright (c) 2013, 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_used;
 
+import 'common/tasks.dart' show CompilerTask;
 import 'common.dart';
-import 'common/tasks.dart' show CompilerTask;
 import 'compile_time_constants.dart' show ConstantCompiler;
 import 'compiler.dart' show Compiler;
 import 'constants/expressions.dart';
 import 'constants/values.dart'
     show
         ConstantValue,
         ConstructedConstantValue,
         ListConstantValue,
         StringConstantValue,
         TypeConstantValue;
-import 'dart_types.dart' show DartType, InterfaceType, TypeKind;
+import 'dart_types.dart' show DartType, InterfaceType;
 import 'elements/elements.dart'
     show
         ClassElement,
         Element,
         ImportElement,
         LibraryElement,
         MetadataAnnotation,
         ScopeContainerElement,
         VariableElement;
 import 'resolution/tree_elements.dart' show TreeElements;
-import 'tree/tree.dart'
-    show Import, LibraryTag, NamedArgument, NewExpression, Node;
+import 'tree/tree.dart' show NamedArgument, NewExpression, Node;
 
 /**
  * Compiler task that analyzes MirrorsUsed annotations.
  *
  * When importing 'dart:mirrors', it is possible to annotate the import with
  * MirrorsUsed annotation.  This is a way to declare what elements will be
  * reflected on at runtime.  Such elements, even they would normally be
  * discarded by the implicit tree-shaking algorithm must be preserved in the
  * final output.
  *
@@ skipping 522 matching lines @@
       // @MirrorsUsed(targets: fisk)
       //                       ^^^^
       //
       // Instead of saying 'fisk' should pretty print the problematic constant
       // value.
       return spannable;
     }
     return node;
   }
 }