Enable the new analysis driver by default, use --disable-new-analysis-driver to disable.

pkg/analysis_server/test/stress/utilities/server.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.
 
 /**
  * Support for interacting with an analysis server that is running in a separate
  * process.
  */
 import 'dart:async';
 import 'dart:collection';
@@ skipping 671 matching lines @@
     if (diagnosticPort != null) {
       arguments.add('--port');
       arguments.add(diagnosticPort.toString());
     }
     if (sdkPath != null) {
       arguments.add('--sdk=$sdkPath');
     }
     if (useAnalysisHighlight2) {
       arguments.add('--useAnalysisHighlight2');
     }
-    if (enableNewAnalysisDriver) {
-      arguments.add('--enable-new-analysis-driver');
+    if (!enableNewAnalysisDriver) {
+      arguments.add('--disable-new-analysis-driver');
     }
 //    stdout.writeln('Launching $serverPath');
 //    stdout.writeln('$dartBinary ${arguments.join(' ')}');
     _process = await Process.start(dartBinary, arguments);
     _process.exitCode.then((int code) {
       if (code != 0) {
         throw new StateError('Server terminated with exit code $code');
       }
     });
     _listenToOutput();
@@ skipping 386 matching lines @@
     if (buffer.length > 0) {
       buffer.writeln();
       buffer.writeln();
     }
     buffer.writeln(filePath);
     _writeErrors('  Expected ', expectedErrors);
     buffer.writeln();
     _writeErrors('  Found ', actualErrors);
   }
 }