Run dart2js tests unmodified in drt.

dart/pkg/unittest/config.dart

Index: dart/pkg/unittest/config.dart
diff --git a/dart/pkg/unittest/config.dart b/dart/pkg/unittest/config.dart
index 34693dde24f6b99fea5b0c1e0c69527979deaec2..5a8b4bcce5c5814b8fd2f5ef45be2087575945bc 100644
--- a/dart/pkg/unittest/config.dart
+++ b/dart/pkg/unittest/config.dart
@@ -37,7 +37,9 @@ class Configuration {
    * tell the vm or browser that tests are still running and the process should
    * wait until they are done.
    */
-  void onStart() {}
+  void onStart() {
+    _postMessage('unittest-suite-wait-for-done');
+  }
 
   /**
    * Called when each test starts. Useful to show intermediate progress on
@@ -121,8 +123,11 @@ class Configuration {
       print('$passed PASSED, $failed FAILED, $errors ERRORS');
     }
 
-    // An exception is used by the test infrastructure to detect failure.
-    if (!success) throw new Exception("Some tests failed.");
+    if (success) {
+      _postMessage('unittest-suite-success');
+    } else {
+      throw new Exception('Some tests failed.');
+    }
   }
 
   String _indent(String str) {
@@ -137,4 +142,10 @@ class Configuration {
   // Currently e.message works in dartium, but not in dartc.
   handleExternalError(e, String message) =>
       _reportTestError('$message\nCaught $e', '');
+
+  _postMessage(String message) {
+    // In dart2js browser tests, the JavaScript-based test controller
+    // intercepts calls to print and listens for "secret" messages.
+    print(message);
+  }
 }