Switch the default from non-driver to driver in several tests

pkg/analysis_server/test/services/completion/completion_target_test.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 test.services.completion.target;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/provisional/completion/dart/completion_target.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../../abstract_context.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(CompletionTargetTest);
   });
 }
 
 @reflectiveTest
 class CompletionTargetTest extends AbstractContextTest {
   Source testSource;
   int completionOffset;
   CompletionTarget target;
 
-  @override
-  bool get enableNewAnalysisDriver => true;
-
   Future<Null> addTestSource(String content) async {
     expect(completionOffset, isNull, reason: 'Call addTestSource exactly once');
     completionOffset = content.indexOf('^');
     expect(completionOffset, isNot(equals(-1)), reason: 'missing ^');
     int nextOffset = content.indexOf('^', completionOffset + 1);
     expect(nextOffset, equals(-1), reason: 'too many ^');
     content = content.substring(0, completionOffset) +
         content.substring(completionOffset + 1);
     testSource = addSource('/test.dart', content);
     AnalysisResult result = await driver.getResult(testSource.fullName);
@@ skipping 554 matching lines @@
     await addTestSource('main() {int b^ = 1;}');
     await assertTarget('b = 1', 'int b = 1');
   }
 
   test_VariableDeclaration_lhs_identifier_before() async {
     // VariableDeclaration  VariableDeclarationList
     await addTestSource('main() {int ^b = 1;}');
     await assertTarget('b = 1', 'int b = 1');
   }
 }