[dart2js] Add helper to detect csp in web tests and use it to set expectations for some tests.

Fixes these: https://dart-ci.firebaseapp.com/#showLatestFailures=true&configurations=dart2js-minified-csp-linux-chrome

Change-Id: I2939e3ce1fdee45d570d038f2f4382747cd617dc
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/436140
Commit-Queue: Nate Biggs <[email protected]>
Reviewed-by: Mayank Patke <[email protected]>

Author: natebiggs

tests/web/csp_helper.dart

@@ -0,0 +1,14 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// 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.
+
+import "dart:js" as js;
+
+final isCspEnabled = (() {
+  try {
+    js.context.callMethod('eval', ['5;']);
+    return false;
+  } catch (e) {
+    return true;
+  }
+})();

tests/web/dart2js/deferred_with_csp_nonce2_test.dart

@@ -10,6 +10,8 @@ import "package:expect/async_helper.dart";
 import "package:expect/expect.dart";
 import "dart:html";
 
+import "../csp_helper.dart";
+
 main() {
   asyncStart();
 
@@ -31,7 +33,11 @@ main() {
     Expect.equals(1, scripts.length);
     for (var script in scripts) {
       Expect.equals("an-example-nonce-string", script.nonce);
-      Expect.equals("an-example-nonce-string", script.getAttribute('nonce'));
+      // nonce attribute not copied through to script when csp enabled.
+      Expect.equals(
+        isCspEnabled ? "" : "an-example-nonce-string",
+        script.getAttribute('nonce'),
+      );
     }
     asyncEnd();
   });

tests/web/dart2js/deferred_with_csp_nonce_test.dart

@@ -10,6 +10,8 @@ import "package:expect/async_helper.dart";
 import "package:expect/expect.dart";
 import "dart:html";
 
+import "../csp_helper.dart";
+
 main() {
   asyncStart();
 
@@ -31,7 +33,11 @@ main() {
     Expect.equals(1, scripts.length);
     for (var script in scripts) {
       Expect.equals("an-example-nonce-string", script.nonce);
-      Expect.equals("an-example-nonce-string", script.getAttribute('nonce'));
+      // nonce attribute not copied through to script when csp enabled.
+      Expect.equals(
+        isCspEnabled ? "" : "an-example-nonce-string",
+        script.getAttribute('nonce'),
+      );
     }
     asyncEnd();
   });