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/language/deferred_constraints_lib.dart b/tools/testing/dart/perf_test_controller.js
similarity index 55%
copy from tests/language/deferred_constraints_lib.dart
copy to tools/testing/dart/perf_test_controller.js
index cdc9d4d8fbddf56553e4e04f5d44eeac2534fa3a..f6990bb65c70cdfd1c31f40dc3422ec04c6ee151 100644
--- a/tests/language/deferred_constraints_lib.dart
+++ b/tools/testing/dart/perf_test_controller.js
@@ -2,10 +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.
 
-class C {}
+/// Helper file to make performance tests run with the Dart browser controller
+/// in test.dart.
 
-class Const {
-  const Const();
-}
-
-const constantInstance = const Const();
+// First import test_controller.js
+dartPrint('unittest-suite-wait-for-done');

[kustermann, 2014/02/27 09:37:15]

I have no idea why you would need this. Why can't you have a base class for all
benchmarks, which prints this before starting the benchmark and prints the
corresponding done message once it's done?

[Emily Fortuna, 2014/02/27 19:27:48]

See my comment at the bottom of this file:
https://codereview.chromium.org/178223008/diff/200001/tools/testing/dart/brow...

But the short version is this is the "wrapper"/glue code around the test to make
it a perf test. All perf tests include this. I don't want to manually modify the
test because the test is also run as a correctness test.