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

pkg/analysis_server/test/abstract_context.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 testing.abstract_context;
 
 import 'dart:async';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 55 matching lines @@
 
   AnalysisDriver get driver {
     if (enableNewAnalysisDriver) {
       return _driver;
     }
     throw new StateError('Should be used with the new analysis driver.');
   }
 
   /**
    * Return `true` if the new analysis driver should be used by these tests.
+   *
+   * Remove this after there are no subclasses that override it.
    */
-  bool get enableNewAnalysisDriver => false;
+  bool get enableNewAnalysisDriver => true;
 
   Source addMetaPackageSource() => addPackageSource(
       'meta',
       'meta.dart',
       r'''
 library meta;
 
 const Required required = const Required();
 
 class Required {
@@ skipping 127 matching lines @@
  * [engine.GeneralizingElementVisitor].
  */
 class _ElementVisitorFunctionWrapper extends GeneralizingElementVisitor {
   final _ElementVisitorFunction function;
   _ElementVisitorFunctionWrapper(this.function);
   visitElement(Element element) {
     function(element);
     super.visitElement(element);
   }
 }