dart2js cleanup: remove unused imports and variables

pkg/compiler/lib/src/tree/nodes.dart

Index: pkg/compiler/lib/src/tree/nodes.dart
diff --git a/pkg/compiler/lib/src/tree/nodes.dart b/pkg/compiler/lib/src/tree/nodes.dart
index 9335fef859d950573231a6ffac2c9611bc51107a..1781c4b398922e2bd449eed2dd50873ac2a5867d 100644
--- a/pkg/compiler/lib/src/tree/nodes.dart
+++ b/pkg/compiler/lib/src/tree/nodes.dart
@@ -5,15 +5,14 @@
 import 'dart:collection' show IterableMixin;
 
 import '../common.dart';
+import '../elements/elements.dart' show MetadataAnnotation;
+import '../resolution/secret_tree_element.dart'
+    show NullTreeElementMixin, StoredTreeElementMixin;
 import '../tokens/precedence_constants.dart' as Precedence show FUNCTION_INFO;
 import '../tokens/token.dart' show BeginGroupToken, Token;
-import '../tokens/token_constants.dart' as Tokens
-    show IDENTIFIER_TOKEN, KEYWORD_TOKEN, PLUS_TOKEN;
-import '../util/util.dart';
+import '../tokens/token_constants.dart' as Tokens show PLUS_TOKEN;
 import '../util/characters.dart';
-import '../resolution/secret_tree_element.dart'
-    show NullTreeElementMixin, StoredTreeElementMixin;
-import '../elements/elements.dart' show MetadataAnnotation;
+import '../util/util.dart';
 import 'dartstring.dart';
 import 'prettyprint.dart';
 import 'unparser.dart';