Fix bug in test_runner.dart

tools/testing/dart/test_runner.dart

Index: tools/testing/dart/test_runner.dart
diff --git a/tools/testing/dart/test_runner.dart b/tools/testing/dart/test_runner.dart
index 41daa58bcb5f263bb0bdc35dfec7ab82f2e874a1..bedc8ef04042e2e2eb6ca0060da9c14fb232bd0b 100644
--- a/tools/testing/dart/test_runner.dart
+++ b/tools/testing/dart/test_runner.dart
@@ -1072,7 +1072,7 @@ class BrowserCommandOutputImpl extends CommandOutputImpl {
         command is BrowserTestCommand &&
         command.browser == "ie11") {
       DebugLogger.warning("Timeout of ie11 on test page ${command.url}");
-      return;
+      return true;
     }
     return false;
   }