Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 30 insertions, 0 deletions

diff --git a/toolkit/components/processsingleton/CustomElementsListener.sys.mjs b/toolkit/components/processsingleton/CustomElementsListener.sys.mjs
new file mode 100644
index 0000000000..2a522d9fe3
--- /dev/null
+++ b/toolkit/components/processsingleton/CustomElementsListener.sys.mjs
@@ -0,0 +1,30 @@
+/* -*-  indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Set up Custom Elements for XUL and XHTML documents before anything else
+// happens. Anything loaded here should be considered part of core XUL functionality.
+// Any window-specific elements can be registered via <script> tags at the
+// top of individual documents.
+Services.obs.addObserver(
+  {
+    observe(doc) {
+      if (
+        doc.nodePrincipal.isSystemPrincipal &&
+        (doc.contentType == "application/xhtml+xml" ||
+          doc.contentType == "text/html") &&
+        // People shouldn't be using our built-in custom elements in
+        // system-principal about:blank anyway, and trying to support that
+        // causes responsiveness regressions.  So let's not support it.
+        doc.URL != "about:blank"
+      ) {
+        Services.scriptloader.loadSubScript(
+          "chrome://global/content/customElements.js",
+          doc.ownerGlobal
+        );
+      }
+    },
+  },
+  "document-element-inserted"
+);