fix: use TrustedHTML to test for customizable <select> support, where necessary (#17743)

https://github.com/sveltejs/svelte/pull/17701#issuecomment-3899991195

no test because jsdom

.changeset/eleven-carpets-learn.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: use TrustedHTML to test for customizable <select> support, where necessary

packages/svelte/src/internal/client/dom/elements/customizable-select.js

@@ -1,5 +1,6 @@
 import { hydrating, reset, set_hydrate_node, set_hydrating } from '../hydration.js';
 import { create_comment, create_element } from '../operations.js';
+import { create_trusted_html } from '../reconciler.js';
 import { attach } from './attachments.js';
 
 /** @type {boolean | null} */
@@ -14,7 +15,7 @@ let supported = null;
 function is_supported() {
 	if (supported === null) {
 		var select = create_element('select');
-		select.innerHTML = '<option><span>t</span></option>';
+		select.innerHTML = create_trusted_html('<option><span>t</span></option>');
 		supported = /** @type {Element} */ (select.firstChild)?.firstChild?.nodeType === 1;
 	}
 

packages/svelte/src/internal/client/dom/reconciler.js

@@ -11,7 +11,7 @@ const policy =
 	});
 
 /** @param {string} html */
-function create_trusted_html(html) {
+export function create_trusted_html(html) {
 	return /** @type {string} */ (policy?.createHTML(html) ?? html);
 }