dart2js cleanup: remove unused imports and variables

pkg/compiler/lib/src/parser/partial_elements.dart

 // Copyright (c) 2015, 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.parser.partial_elements;
 
 import '../common.dart';
 import '../common/resolution.dart' show Parsing, Resolution;
 import '../dart_types.dart' show DynamicType;
 import '../elements/elements.dart'
     show
         CompilationUnitElement,
-        ConstructorElement,
         Element,
         ElementKind,
         GetterElement,
-        LibraryElement,
         MetadataAnnotation,
-        MethodElement,
         SetterElement,
         STATE_NOT_STARTED,
         STATE_DONE;
 import '../elements/modelx.dart'
     show
         BaseFunctionElementX,
         ClassElementX,
         ConstructorElementX,
         DeclarationSite,
         ElementX,
-        FieldElementX,
         GetterElementX,
         MetadataAnnotationX,
         MethodElementX,
         SetterElementX,
         TypedefElementX,
         VariableList;
 import '../elements/visitor.dart' show ElementVisitor;
-import '../tokens/token.dart'
-    show
-        BadInputToken,
-        BeginGroupToken,
-        ErrorToken,
-        KeywordToken,
-        StringToken,
-        Token,
-        UnmatchedToken,
-        UnterminatedToken;
+import '../tokens/token.dart' show Token;
 import '../tokens/token_constants.dart' as Tokens show EOF_TOKEN;
 import '../tree/tree.dart';
-
 import 'class_element_parser.dart' show ClassElementParser;
-import 'parser.dart' show Parser;
 import 'listener.dart' show ParserError;
 import 'member_listener.dart' show MemberListener;
 import 'node_listener.dart' show NodeListener;
+import 'parser.dart' show Parser;
 
 abstract class PartialElement implements DeclarationSite {
   Token beginToken;
   Token endToken;
 
   bool hasParseError = false;
 
   bool get isMalformed => hasParseError;
 
   DeclarationSite get declarationSite => this;
@@ skipping 391 matching lines @@
       } on ParserError catch (e) {
         partial.hasParseError = true;
         return new ErrorNode(element.position, e.reason);
       }
       Node node = listener.popNode();
       assert(listener.nodes.isEmpty);
       return node;
     });
   });
 }