Replace run_selenium.py with Dart script that uses the browser controller for performance tests.

tools/testing/dart/perf_test_controller.js

Index: tools/testing/dart/perf_test_controller.js
diff --git a/tests/compiler/dart2js/path with spaces/library space/part space/part space.dart b/tools/testing/dart/perf_test_controller.js
similarity index 55%
copy from tests/compiler/dart2js/path with spaces/library space/part space/part space.dart
copy to tools/testing/dart/perf_test_controller.js
index 58aff0fb6e8a8e53197e400cf859718ce5e65606..f6990bb65c70cdfd1c31f40dc3422ec04c6ee151 100644
--- a/tests/compiler/dart2js/path with spaces/library space/part space/part space.dart	
+++ b/tools/testing/dart/perf_test_controller.js
@@ -2,6 +2,8 @@
 // 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.
 
-part of spaces;
+/// Helper file to make performance tests run with the Dart browser controller
+/// in test.dart.
 
-bar() => 499;
+// First import test_controller.js
+dartPrint('unittest-suite-wait-for-done');