Fix couple hints.

pkg/analyzer/test/src/task/dart_test.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 analyzer.test.src.task.dart_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 15 matching lines @@
 import 'package:analyzer/task/dart.dart';
 import 'package:analyzer/task/general.dart';
 import 'package:analyzer/task/model.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 import 'package:unittest/unittest.dart';
 
 import '../../generated/resolver_test_case.dart';
 import '../../generated/test_support.dart';
 import '../../utils.dart';
 import '../context/abstract_context.dart';
-import '../context/mock_sdk.dart';
 
 main() {
   initializeTestEnvironment();
   defineReflectiveTests(BuildCompilationUnitElementTaskTest);
   defineReflectiveTests(BuildDirectiveElementsTaskTest);
   defineReflectiveTests(BuildEnumMemberElementsTaskTest);
   defineReflectiveTests(BuildExportNamespaceTaskTest);
   defineReflectiveTests(BuildLibraryElementTaskTest);
   defineReflectiveTests(BuildPublicNamespaceTaskTest);
   defineReflectiveTests(BuildSourceExportClosureTaskTest);
@@ skipping 5606 matching lines @@
   /**
    * Fill [errorListener] with [result] errors in the current [task].
    */
   void _fillErrorListener(ResultDescriptor<List<AnalysisError>> result) {
     List<AnalysisError> errors = task.outputs[result] as List<AnalysisError>;
     expect(errors, isNotNull, reason: result.name);
     errorListener = new GatheringErrorListener();
     errorListener.addAll(errors);
   }
 }