dart2js cleanup: remove unused imports and variables

pkg/compiler/lib/src/patch_parser.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.
 
 /**
  * This library contains the infrastructure to parse and integrate patch files.
  *
  * Three types of elements can be patched: [LibraryElement], [ClassElement],
  * [FunctionElement]. Patches are introduced in patch libraries which are loaded
  * together with the corresponding origin library. Which libraries that are
@@ skipping 98 matching lines @@
  * - Builders shift between declaration and implementation depending on usages.
  * - Compile-time constants use constructor implementation exclusively.
  * - Work on function parameters is performed on the declaration of the function
  *   element.
  */
 
 library dart2js.patchparser;
 
 import 'dart:async';
 
-import 'constants/values.dart' show ConstantValue;
+import 'common/tasks.dart' show CompilerTask;
 import 'common.dart';
 import 'compiler.dart' show Compiler;
-import 'common/tasks.dart' show CompilerTask;
+import 'constants/values.dart' show ConstantValue;
 import 'dart_types.dart' show DartType;
 import 'elements/elements.dart';
 import 'elements/modelx.dart'
     show
         BaseFunctionElementX,
         ClassElementX,
         GetterElementX,
         LibraryElementX,
-        MetadataAnnotationX,
         SetterElementX;
 import 'id_generator.dart';
 import 'js_backend/js_backend.dart' show JavaScriptBackend;
 import 'library_loader.dart' show LibraryLoader;
 import 'options.dart' show ParserOptions;
+import 'parser/element_listener.dart' show ElementListener;
 import 'parser/listener.dart' show Listener, ParserError;
-import 'parser/element_listener.dart' show ElementListener;
 import 'parser/member_listener.dart' show MemberListener;
+import 'parser/parser.dart' show Parser;
 import 'parser/partial_elements.dart' show PartialClassElement;
 import 'parser/partial_parser.dart' show PartialParser;
-import 'parser/parser.dart' show Parser;
 import 'scanner/scanner.dart' show Scanner;
 import 'script.dart';
 import 'tokens/token.dart' show StringToken, Token;
 
 class PatchParserTask extends CompilerTask {
   final String name = "Patching Parser";
   final ParserOptions parserOptions;
 
   PatchParserTask(Compiler compiler, this.parserOptions) : super(compiler);
 
@@ skipping 459 matching lines @@
 
 class PatchVersion {
   final String tag;
 
   const PatchVersion(this.tag);
 
   bool isActive(String patchTag) => tag == null || tag == patchTag;
 
   String toString() => 'PatchVersion($tag)';
 }