[dart2js] Make --benchmarking-x imply --csp

This is a temporary assignment of the meaning of `--benchmarking-x`.

Change-Id: I453aca3fa2782498664aad05f0d637af5e91bd34
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/168402
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Commit-Queue: Stephen Adams <sra@google.com>
diff --git a/pkg/compiler/lib/src/options.dart b/pkg/compiler/lib/src/options.dart
index 6d336a5..0f51b54 100644
--- a/pkg/compiler/lib/src/options.dart
+++ b/pkg/compiler/lib/src/options.dart
@@ -534,6 +534,7 @@
     if (benchmarkingExperiment) {
       // Set flags implied by '--benchmarking-x'.
       // TODO(sra): Use this for some NNBD variant.
+      useContentSecurityPolicy = true;
     }
 
     if (_noLegacyJavaScript) legacyJavaScript = false;