reuse the same browser when running webdriver tests

tools/testing/dart/test_suite.dart

 // Copyright (c) 2012, 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.
 
 /**
  * Classes and methods for enumerating and preparing tests.
  *
  * This library includes:
  *
  * - Creating tests by listing all the Dart files in certain directories,
@@ skipping 515 matching lines @@
           // No compilation phase.
           compilerExecutable = null;
           compilerArgs = null;
           break;
         default:
           Expect.fail('unimplemented component $component');
       }
 
       List<String> args;
       if (component == 'webdriver') {
-        args = ['$dartDir/tools/testing/run_selenium.py', '--out=$htmlPath',
+        args = ['$dartDir/tools/testing/run_selenium.py',
+            '--browser=${configuration["browser"]}',
             '--timeout=${configuration["timeout"] - 2}',
-            '--browser=${configuration["browser"]}'];
+            '--out=$htmlPath'];
       } else {
         args = [
             '$dartDir/tools/testing/drt-trampoline.py',
             dumpRenderTreeFilename,
             '--no-timeout'
         ];
         if (component == 'dartium') {
           var dartFlags = ['--ignore-unrecognized-flags'];
           if (configuration["checked"]) {
             dartFlags.add('--enable_asserts');
@@ skipping 575 matching lines @@
  * $noCrash tests are expected to be flaky but not crash
  * $pass tests are expected to pass
  * $failOk tests are expected to fail that we won't fix
  * $fail tests are expected to fail that we should fix
  * $crash tests are expected to crash that we should fix
  * $timeout tests are allowed to timeout
 """;
     print(report);
    }
 }