dart2js cleanup: remove unused imports and variables

pkg/compiler/lib/src/resolution/signatures.dart

 // Copyright (c) 2014, 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.signatures;
 
 import '../common.dart';
 import '../compiler.dart' show Compiler;
 import '../dart_types.dart';
 import '../elements/elements.dart';
 import '../elements/modelx.dart'
     show
         ErroneousFieldElementX,
         ErroneousInitializingFormalElementX,
         FormalElementX,
-        FunctionElementX,
         FunctionSignatureX,
         InitializingFormalElementX,
         LocalParameterElementX;
 import '../tree/tree.dart';
 import '../universe/use.dart' show TypeUse;
 import '../util/util.dart' show Link, LinkBuilder;
-
 import 'members.dart' show ResolverVisitor;
 import 'registry.dart' show ResolutionRegistry;
 import 'resolution_common.dart' show MappingVisitor;
 import 'scope.dart' show Scope;
 
 /**
  * [SignatureResolver] resolves function signatures.
  */
 class SignatureResolver extends MappingVisitor<FormalElementX> {
   final ResolverVisitor resolver;
@@ skipping 398 matching lines @@
 
   DartType resolveReturnType(TypeAnnotation annotation) {
     if (annotation == null) return const DynamicType();
     DartType result = resolver.resolveTypeAnnotation(annotation);
     if (result == null) {
       return const DynamicType();
     }
     return result;
   }
 }