Don't run Analysis Server performance tests in checked mode.

pkg/analysis_server/benchmark/perf/performance_tests.dart

Index: pkg/analysis_server/benchmark/perf/performance_tests.dart
diff --git a/pkg/analysis_server/benchmark/perf/performance_tests.dart b/pkg/analysis_server/benchmark/perf/performance_tests.dart
index 6d301c923303be140c11c2924387bcd2fb19c5d2..d6be917b314bf1c6fea03ff7287d4847e45bb8bb 100644
--- a/pkg/analysis_server/benchmark/perf/performance_tests.dart
+++ b/pkg/analysis_server/benchmark/perf/performance_tests.dart
@@ -46,7 +46,7 @@ abstract class AbstractAnalysisServerPerformanceTest
       expect(serverConnected.isCompleted, isFalse);
       serverConnected.complete();
     });
-    return startServer().then((_) {
+    return startServer(checked: false).then((_) {
       server.listenToOutput(dispatchNotification);
       server.exitCode.then((_) {
         skipShutdown = true;